DotA Roles
In Dota, Dota2, roles define the way a hero can be played given their Attributes, Skills, and Items. Different heroes are suited for different roles and can be played in a variety of ways based on a player's preference and the team's composition. It is important to know how to effectively play a hero in many roles, as this increases the flexibility of your team, especially in a competitive draft setting.
Lane Support "Helpful in the early-game laning in protecting your team's carry."
Lane Supports are Heroes who help their team's Carry control the lane in the early stages of the game. They are able to either repel enemies from your team's carry or to allow the carry to continually stay in the lane using abilities that replenish either health or mana. Common traits of Lane Supports are long-ranged right-click attacks and abilities that are highly useful from level 1 and up. They should always lane with the team's Hard Carry, as aside from supporting them; their lack of dependence on gold and levels means said Carry can take all the farm for themselves without running the risk of soloing a lane.
Examples: Dazzle, Lich, Omniknight.
Carry "Will become more useful later in the game if they gain a significant gold advantage."
Also known as a "Hard(core) Carry" (as opposed to a "Semi-Carry"), a Carry is the hero that a team rallies around late game. (The role's name is derived from the act of "carrying" a team; that is, to bear the responsibility for ultimate victory.) They are the ones expected to have the highest number of hero kills for their teams. Carries typically lack early game power, but they have strong scaling skills; thus, they are highly dependent on items in order to be successful. In addition, Carries often have a built-in escape mechanism. Usually, carries rely on strong and fast physical attacks, but this is not always the case. Having more than one Carry will cause competition within your team for resources, which typically results in a number of underpowered Carries. For this reason it is highly recommended that a team have only one Hard Carry, because as the game progresses a hard carry must begin to secure the majority of kills for themself. Any Semi-Carries (heroes [usually Gankers/Nukers] that have attained sufficient level and gold advantage to avoid diminishing in the late game; see below) must be prepared to forfeit kills to the Hard Carry when they are able after the early game. Supports and Initiators should never take a kill unless they are the only person capable of executing it.
Carries typically are relegated to a side lane early on with one or more Support/Babysit heroes to babysit them until they collect the necessary items to farm independently.
Examples: Anti-Mage, Faceless Void, Phantom Assassin.
Disabler "Has a guaranteed disable for one or more of their spells."
Disablers are Heroes whose abilities are more focused to reliable crowd control, whether by single target or by area. Though fundamentally Support, they can act as Initiator in a gank when the number of enemy Heroes to be killed is few in number - a true Initiator's cooldowns are best saved for a large confrontation.
Examples: Bane, Lion, Shadow Shaman.
Ganker Gankers are Heroes with abilities that deliver long duration crowd control or immense damage early in the game. Their goal is to give the team an early game advantage during laning phase by killing enemy heroes in their proper lanes. Many Gankers become Semi-Carries if they are successful in their efforts, owing to a large gold and level advantage; but because their abilities do not scale they will usually suffer in late game (hence the need for a Hard Carry).
Examples: Bloodseeker, Night Stalker, Queen of Pain.
Initiator "Good at starting a teamfight."
Initiators are heroes who can safely and advantageously start a team fight. These heroes typically have strong area of effect damage or disable or some skill to affect the positioning of the enemy team. Although it is common for an Initiator to be a Tank, this is not always the case; heroes such as Vengeful Spirit can attempt a "suicide swap" to isolate and quickly eliminate an enemy Carry, which will lure the enemy team - thus "initiation".
Examples: Tidehunter, Enigma, Sand King.
Jungler"Can farm effectively from neutral creeps inside the jungle early in the game."
Junglers are heroes that can jungle neutrals at the start of the game, rather than lane. This allows for there to be two solo lanes, which in turn allows two allies to benefit from solo farm instead of one. Junglers typically have skills that allow them to convert neutral creeps, summon minions, or sustain themselves through damage; and the ability to Jungle is found in Heroes of all classes.
Although having two solo lanes and a Jungler produces a significant gold and experience advantage, it increases exposure to enemy ganks. To alleviate this, make sure your second solo hero is a Semi-Carry in the long lane (bottom for Radiant and top for Dire). This way, the creeps fight closer to the tower and the Jungler can quickly come to his aid or gank; there is a reason why this lane is called the "safe lane" and the other side lane the "suicide lane".
Examples: Chen,Lycanthrope, Nature's Prophet, Axe.
Pusher "Can quickly siege and destroy towers and barracks"
Pushers are heroes who focus on bringing down towers quickly, thereby acquiring map control. If they succeed, they often shut down the enemy carry by forcing them away from farming. They typically have skills that fortify allied creep waves, summon minions, or deal massive amounts of damage to enemy towers.
Examples: Broodmother, Leshrac, Venomancer.
Roamer "Can focus on moving around the map instead of farming creeps early in the game."
Their main focus is gaining as much map control early in the game by warding and studying location of missing Heroes. They are also responsible for creep pulling, creep stacking (for the purpose of helping a fellow Jungler or to be the source of farm) and most crucially shutting down enemy Junglers.
Examples: Crystal Maiden, Earthshaker, Vengeful Spirit.
Tank "Has the ability to last longer in teamfights."
Tanks are heroes with large amounts of HP, HP regeneration, and armor; thus the ability to take high amounts of damage. However, gearing for this deprives the unit of offensive items, and so their damage output is generally lower. Typically, Tanks fill other secondary roles, usually Initiator. As most Heroes have no true way to force enemies to attack them (Axe being the sole exception), most use their disables to peel for their carries.
Examples: Axe, Dragon Knight, Skeleton King, Centaur.
Escape Escape heroes are heroes equipped with one or more escape mechanisms which allow them (or sometimes their allies) to avoid damage and abilities while retreating or repositioning themselves during a teamfight or gank. Escape heroes are particularly suited to soloing the "suicide lane" or short lane, as they can turn situations where death is inevitable into a temporary delay in farm. Escape mechanisms include movement speed buffs, invisibility, teleportation, and evasion.
Examples: Mirana, Puck, Weaver
Semi-Carry Semi-Carries are heroes with strong early or middle game power that drop off later in the game. These heroes are not as item dependent as a typical Carry and can function with a few core items. Furthermore, because of their lack of item dependence, Semi-Carries often purchase utility items. Early on, the Semi-Carries typically take the lead in asserting map control to allow the Carry to farm. They transition later on into a more supportive role.
A Semi-Carry will often take the middle lane, allowing him access to both side lanes. A team typically has multiple Semi-Carries, depending on the laning strategy. If there is a Jungler, expect to see a Semi-Carry solo in the long lane (bottom for Radiant and top for Dire).
Many Ganking heroes transition into a Semi-Carry role if they do well at killing other heroes in the early/mid game.
Examples: Tinker, Windrunner.
Support "Can focus less on amassing gold and items, and more on using their abilities to gain an advantage for the team."
Supports are heroes whose purpose is to keep their allies alive and give them opportunities to earn more gold and experience. Supports will usually come with skills, such as healing spells or skills that disable enemies; and generally have low damage output (but often with a powerful-yet-situational nuke). Like Semi-Carries, Supports are not dependent on items (with some exceptions), and thus, most of their gold will be spent on items for the benefit of the team such as Animal Courier, Observer Ward, Sentry Ward, and Smoke of Deceit.
Supports are typically paired with the team's Carry at the start of a game. This is because the Carry tends to be the weakest and most gold-hungry member of the team early on. A Support should always forfeit kills to the team's Carry, only performing a kill if none of his allies are able to do it.
Examples: Ancient Apparition, Warlock, Witch Doctor.
C/P DotA2wiki
It will help some people to understand that there are couple more roles then just carry/wannabe carry.
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