Watch live coverage of the 2015 World Championship from Wembley Arena.
League of Legends is a team game, with each member of the five-member team taking on the role of a particular character or Champion online.
Each team member operates his own Champion. Different Champions or on-screen characters have different characteristics - one may be powerful but with little stamina, so he, or she, or it, is good at killing, but can't last, and so is more likely to be killed once time has passed.
The aim is for one side to kill the Champions of the other and to achieve goals like capturing a turret in a fortress.
This is available to UK users only.
This is a live BBC Sport stream, due to start at 14:00 BST