Patch

Patch (otherwise known as Client Version), are accompanied by the Patch Notes are the set of information in which a patch is delivered. Every patch contains the following modifications:
 * Balance changes: Bi-weekly changes to even out the power balance between Champions.
 * League of Legends and PVP.net features: Anything new that you will experience on PVP.net or in the game.
 * New content: New or remade Champions, Items, or Skins.
 * Bug fixes: Both from the forums and internally.
 * Backend/development changes: Technology or configuration changes that go on behind the scenes.

List of patches
Below is a table noting the recognizable events from each, and a link to their patch notes.