have created -- Present Perfect, Active Voice have been created -- Present Perfect, Passive Voice

"Could somebody explain to me what the difference is between..." Be careful of word-order in indirect questions. ;) The difference is basically passive voice. This is where the subject receives the action, instead of performing the action. "After you have been created" is a complete clause and means someone/something else creates you. The subject received the action. "After you have created" is incomplete. We need to know what you have created. However, here the subject performs the action.

"After you have been created" is referring to you, so it means after you were made, however this is not commonly used to refer to a human unless you are reading something about robots :) "After you have created" is referring to an action you are doing, so it means that after you have completed making something (whatever the creation is). Hopefully this clarifies it :)

"You have created something." and "Something has been created by you." means the same. I hope that helps.