What are the main theories regarding the Rapture?

In a previous post (since deleted), a commenter asked whether my question was regarding a pre Tribulation, in Tribulation, or post Tribulation theory of the Rapture. I was confused on this point, which is one reason I deleted the question, and am asking this one instead. Matthew 5:13 says: "13 “You are the salt of the earth, but if salt has lost its taste, how shall its saltiness be restored? It is no longer good for anything except to be thrown out and trampled under people's feet." I believe that this may be a reference to the world getting worse after the Rapture removes the better people from the world. I would like an overview of the main theories regarding the Rapture, and which Christian sects believe which version.