Basically, a red dot sight mounts just like a scope. On/Off switch usually provides several different levels of brightness of the dot so you can adjust for the level of light where you are shooting and, if the sight offers both red and green dots, allows you to switch between them. Obviously, the sight is turned off when not in use and many sights offer automatic Off after some reasonable period of time. Zeroing of the sight works just like a scope. The sights are great for quick target acquisition, both eyes staying open and a wide field of view being provided, but usually aren't great for precision target shooting unless the dot is very small. What else would you like to know?Here is a link that provides a lot of information about both red dots and holographics. https://www.pewpewtactical.com/red-dots-vs-holographic-sights/
sometimes they have open box for $50.00. https://www.at3tactical.com/products/at3-rd-50-micro-red-dot-reflex-sight Reticle: 2 MOA Red Dot