Bot in League of Legends refers to computer controlled opponent ( AI - Artificial Intelligence) available in custom games and co-op vs. AI matches. Bots can have either "beginner" or "intermediate" AI.
On January 24, 2012 it was announced that the bot system would be expanded with more bots, better intelligence and availability on the Crystal Scar
. On February 01, 2012, the system was released. 
Bots can be used for:
Practicing against or learning how to play a new Champion;
Filling in for missing players to even out teams;
Leisurely play for those who do not want to experience such competition between summoners;
New players who want to familiarize themselves with the game (champions, maps, items, item builds, champion skills, strategies etc.) before competing with other summoners.
Runes and Masteries Edit
Intermediate bots take 15 mastery points and have 16 runes--five each of Tier 2 Marks/Seals/Glyphs and one Tier 2 Quintessence. Intermediate bots have no increased stats except for a boost to their passive gold gain.
Beginner bots have neither runes nor masteries.
Available Bots Edit
On January 24, 2012 it was announced that new bots would be added to the existing pool.
This was implemented on  February 01, 2012.
Since this update are 54 of 116 (46.55%) champions available as bots.
Champions with a
were available prior to the V220.127.116.11 update.
Bots available in Custom Game Edit
Custom Games only support beginner level bots (29 of 116 = 25%).
Dominion-exclusive Bots Edit
Some bots have been only sighted in Dominion mode.
Adding Bots Edit
To add a bot into a practice game, you must first be the creator or the host of the game. Then, click the "Add Bot" button on the right of the empty slot to add a bot to the corresponding team. Once a bot has been added, you can then change the Champion of the bot by selecting it from the drop-down menu.
Tutorial Bots Edit
In the new tutorial, Battle Training, four new bots appeared, with a high AI, these are:
, who plays on the player's team, and Shen , Annie , and Malphite , who opposed the player.
Cancelled Bots Edit
During release in patch Sona's V18.104.22.168, she was unintentionally added onto the bot roster. Bots' names are usually made up of the champion name followed by the word "Bot" (e.g. Annie Bot). However, went by the name "game_bot_sona". She did nothing but autoattack and she was removed from the bot roster with Sona V22.214.171.124. She has been reintroduced as a standard bot with the Rise of the Bot Army update.
After the update, and Nasus appear to be scheduled for removal as bots. However, it is possible that they will still be able to be selected in custom games, but won't be available in random player vs AI games. They, together with Alistar and Malphite , were unavailable in that mode before the update.
Patch History Edit
bot will no longer do nothing which occurred when the target of Shen Stand United was killed while Shen was channeling.
Added Bot for all Co-op vs AI maps.
Jarvan IV Bots may now make chat messages.
Improved retreat logic for bots with dashes.
Added Bot for all Co-op vs AI maps.
Darius Bots are more likely to use items with actives.
Twisted Treeline bots should now favor defending their base over taking altars.
Twisted Treeline bots no longer get stuck at the summoning platform when an inhibitor is under attack.
Custom game Summoner's Rift bots now use the same push logic as beginner Co-op vs. AI bots, which should address several issues of bots getting stuck on the map.
Added a pathing workaround to prevent Summoner's Rift bots from getting trapped in certain areas of the map (e.g. Baron pit).
Battle Training bots should no longer get stuck during the tutorial.
will now increase the damage of Vorpal Spikes when he levels it up.
Cho'Gath Bot will now appear on intermediate difficulty in Co-op vs AI for all maps.
Veigar Bot Fixed a bug where Summoner's Rift bots would occasionally get stuck on the summoning platform after respawn if enemy champions were nearby.
Fixed a bug where would idle while trying to attack enemy minions.
Kayle Bot Bots now properly factor untargetable enemy turrets in threat calculations, making it harder to get them stuck between towers.
Intermediate bots now have a chance to use a random skin.
Custom game bots now lane properly when allied players are jungling.
Changed the way bots evaluate towers to better take into account minions and enemies.
Changed return to base logic for bots to make them more likely to heal and purchase items.
Dominion bots should now properly ignore invisible units when deciding to defend capture points.
Beginner bots are now less likely to assist each other during kill and retreat situations.
Bot assist logic now works during the laning phase.
Updated item build.
Ashe Bot's should now properly purchase Master Yi Bot on Dominion instead of Sanguine Blade .
Bots are now more likely to use abilities while retreating.
Bots now properly retreat in their base to the summoning platform instead of getting stuck between the nexus turrets.
Bots no longer forget they are being chased.
no longer occasionally cancels Malzahar Bot Nether Grasp.
Added and Alistar to the bot roster.
Dr. Mundo Intermediate bots will now sell their Doran's items to buy an additional item after completing their builds.
Beginner bots will no longer purchase elixirs.
Updated several bots' item builds.
Bots will no longer kill themselves by chasing enemies onto the summoning platform.
Fixed a bug where would occasionally get stuck toggling Ashe Bot Frost Shot repeatedly.
Fixed a bug where did not learn all of his abilities.
Shen Bot Fixed a bug where bots would use on knockup and knockback abilities.
Changed Soraka Bot's Wish logic to help all allies instead of just those near her.
Changed logic for use of Master Yi Bot's Meditate.
Fixed a bug where Dominion bots would prematurely break counter-channel attempts on neutral points.
Fixed a bug where did not learn all of her skills.
Added and Sion to the bot roster.
Vladimir Improved bots' target acquisition while near enemy towers to reduce the amount of tower diving.
Improved bots' logic for assisting each other.
Bots now properly purchase elixirs after finishing their item builds.
Fixed a bug where bots would sometimes randomly path toward the enemy base.
Improved cast logic on ultimates for and Caitlyn Bot .
Lux Bot Fixed a bug where bots in Dominion would sometimes idle under enemy capture points.
Added to the bot roster.
Blitzcrank Improved bots' ability to last hit and reduced how much they push their lanes.
Reduced the amount of gold given to bots on Summoner's Rift intermediate.
Added the ability for bots to call for help from nearby bots.
Improved the precision of skillshots and ground targeted AoE abilities.
Minor bug fixes with , Leona Bot , and Lux Bot .
Rise of the Bot Army:
Players can now queue to play against a much wider roster of champions in Co-op versus AI.
You can see the complete list of added bots here.
Bottom and top lane champions switched. The AD carry and support now go to the bottom lane while the tank and bruiser AI go to the top lane.
NEW Co-op vs. AI:
This mode pits a team of all human players against a team of all AI bots on Summoner's Rift.
The following bots are enabled for Co-op vs. AI: , Annie , Ashe , Cho'Gath , Miss Fortune , Nunu , Renekton , Ryze , Shen , Soraka , Taric , and Trundle .
Bots will now properly respond to taunts.
Bots are now properly labeled at the difficulties of "new player" and "easy".
May 9, 2009 Patch: