I'm new to DMing and to the D&D world in general. I am setting up my next session and I need to get the monsters ready. The campaign I am using is "The Battle of Gib Rus." I am not sure what some of the acronyms are. For example they need to fight some trolls and it reads as follows.
"Trolls [5]: AC4, MV. 12", HD 6+6, #AT 3, Dmg. 5-8/5-8/2-12, THAC0 13. "
Now I know what some of that means (or believe to know) but unsure of how to use the information given. I know Dmg means Damage but how do those numbers come into play.
I guess what I am asking is can someone explain this to me like I was 5. I feel like once I get a grasp on this first encounter the rest should fall into place.

Thanks .