AR-15s

thx for tolerating my stupid noobee questions lol

what it the difference between Weaver, Piccatiny, and MLOK?

thoughts on this? say holographic, what does that mean?
GGD Holographic Red/Green Dot Reflex Sight

Holographic is fine too. I would not buy one of those though, those are el cheapo and can break easily.

I would recommend Eotech or Holosun, Leupold etc.. They are pricey though.