Hard Carries require a lot of support and farming gold, but will "carry" the team to victory later in the game. They tend to be "Late Game" heroes with high Damage Per Second (DPS) and abilities that scale well into late game.
- Farm/Item Dependent (they need a lot of gold and items)
- Generally Start off weaker, but will snowball
- Generally have abilities that scale well (e.g. Critial Hits, % based damage)
- Generally Damage Per Second (DPS) focused
Support heroes usually do not deal a lot of damage, but enable others to perform more effectively. Most have some sort of crowd control ability, in that they make their opponents deficient in some way. Support is usually responsible for buying "support items" like Wards, Couriers, as well as items they provide utility like Force Staff.
- Generally do not need levels, gold, or items to be effective
- Generally have supportive spells like crowd control (e.g. Stun, Silence), Auras (e.g. increased mana regen, bonus damage)
The Pusher's main role is to take down towers and structures. This is usually accomplished by innate abilities such as being able to summon minions or damage structures with spells.
- Able to take down towers with ease
- Generally have summons/minions or spells that damage structures
The Initiator is the first hero into battle. They do this by using an ability that will either disable the entire enemy team, do a large amount of damage before they can be stopped, and sometimes almost instantly take out one core enemy.
- Have the ability to enter battle first without dying
- Generally have a spell with a large Area of Effect (AoE)
- Generally have a spell that can disable (e.g. Stun, Silence) enemies
- Sometimes have an innate ability to get close to enemies quickly or without being noticed (e.g. Invisibility, Movement Spells)
- Many benefit from having a Blink Dagger
Gankers are tasked with suprising a lane with an attack. Most gankers are able to either control the enemies they are attacking with stuns, or instantly tear through them with high damage nukes.
- Benfit from early farm or levels (i.e. generally being solo at the middle lane is beneficial for them)
- Have spells that have high burst damage and/or crowd control (e.g. mostly Stuns)
- Sometimes have high mobility
Roamers are similar to gankers except that they usually stay out of lane, moving from lane to lane to set up ganks. This allows for an additional her to take solo farm and levels.
- Level independent
- Have strong crowd control ability
These are probably the terms you'll hear the most. Many heroes fit into more than one category. There are also some mashups you'll hear like "Semi-Carry", which are heroes that aren't necessarily as proficient at carrying as a hard carry, but still have the ability to do so (e.g. Mirana).