Boost

A boost temporarily increases the amount of Influence Points or Summoner Experience Points gained at the conclusion of each match. There are two kinds of boosts: duration boosts and win boosts. Each of them can be bought from the Riot Store using Riot Points or received from Riot (often compensatorily).

Duration boosts
Duration boosts are active for a certain amount of time (for example, 1 day). Duration boosts double the base amount of IP received for any type of game win or lose, not counting other bonuses. Examples of those other bonuses which are not doubled include the first win of the day bonus, the match-made game bonus, or a bonus from another boost.

Per win boosts
Per win boosts are only applied if you win a game – they will never expire. Per win boosts give you a flat amount of IP equivalent to the max base IP you can earn from a game (values are different for each game mode). This change was made to ensure players were getting the most out of their boost for extremely short games, but Riot hasn't updated the explanations of how per win boosts work. Because of how per win boosts work, they will give much less IP for Dominion, Custom, Twisted Treeline and Co-op vs. AI games.

Available boosts
The Riot Store offers boosts for a specified number of wins and for specified durations.

Free boost

 * If you combine a duration boost and a per win boost, you will receive both bonuses as long as both are active.
 * During special events, Riot has given the community free IP boosts.