MMORPG Bots are basically third-party programs used in MMORPGs to gain experience, items, or other virtual supplies without having the user play. Basically, it is used for undesirable purposes that is simply called 'cheating'. There are many MMORPG Bots, that have enabled people to sell the earned in-game currency for real life profits.
Bots are not usually permitted, but Magic World Online, Angels Online and Shattered Dimension Online have become the first few MMORPGs to come with and allow Bots. GodsWar Online has a programmed bot in its client known as AFK mode.
Bots may or may not cause damage to the game client. But, as stated above, there have been many games which permit usage of bots.