Heroes are the essential element of Dota 2, as the course of the game is dependent on their intervention. Players are split into two teams of 5, and can select a Hero from a selection panel. Heroes all have different play styles that stem from unique Skills and combinations of Attributes. Over the course of the game, Heroes will accumulate Experience. Once a Hero has enough experience, they will level up, making them more powerful than before and allowing them to train new Skills. Most Heroes have a distinct Role that defines how they can affect the battlefield, though many Heroes can perform two or more of these Roles. Currently, 102 of the 112 heroes are playable in the main Dota 2 client.
You can also view the heroes in a more compact grid which is the same as the in-game learn tab on the Hero Grid page.