Literally, word by word, means "Okay bye now. Good luck and have fun with whatever you gonna do today. Also, thanks for your time." These word abbreviates into the shorten form 'kkbyeglhfthx', similar to that of 'lol'. It is a versatile word that can be used in any occasion because of the many expressions and intentions that can be associated with it.
Its often (rarely actually) used in chatting and online-gaming. The word can also be mix, drop and match with other short forms to suit your needs. For example, if you had a great game and now taking your leave, you may add 'gg'(good game) and maybe drop 'glhf' from it, hence making 'kkbyeggthx' (Okey bye gotta go now. Good game and thanks for the fun time). Trivia: First used and introduced by the originator, who is a weird-asian psychopath, whose initial is 'F'.
ProGamer: "OMG arabz why do you have to disconnect now?"