What is the difference between abandoning and resigning games?

First of all I would like to tell that I never abandon games.I always either resign or get checkmated.But still this doubt strikes me.What is the difference between abandoning and resigning?Both mean that my opponent has outplayed me and I want to continue the game no more.So I give up.Right?But I have seen many people fume because people abandon instead of resigning.Ok maybe it is against the guidelines but it doesnt make a huge lot of difference does it?Pls explain.

Abandonment make the opponent wait for the timeout mechanism. Resignation allows both players to move in to their next game.

But I have seen many of my games end the moment they abandon I dont have to wait.

It depends on exactly what happens and the client being used but in most cases there's a wait