[quote=@Thaddeus Dron]
Now I am curious as to what a collab post is, and how it differs from the everyday back and forth Rp. 
[/quote]

It's essentially the same as what you said what it differs from. The main difference is that, while back-and-forth posting is indeed like collab posts, the latter acts more like a chapter in a book rather than machinegun-posting.