halo red dot sight

Hello, I am thinking that I would like to buy and mount an A1 Optic Halo Red Dot Reflex sight on my 1 year old Mini-14 .223 Tactical rifle. It says that it mounts to a 7/8" Weaver style rail or mount. I'm not sure what that is and how it would mount on my gun. I have a lot of guns but don't...