A few different things going on with a Semi auto.
Striker fired vs hammer fired. Hammer position is very easy to see condition of pistol. Striker is a bit less open to elements less likely to snag, rarely has a second strike option ( largly considered unuseful anyway).
Single stack magazine Vs. double stack. Singles are usually prefered by those with smaller hands, but a double will hold much more ammo. As a ccw single can dissapear easier, A good holster and a bit of thought towards wardrobe will usually make a double hide well.
Single action, 1911 style manual safety, and a light trigger pull. Double action, revolver style heavy trigger pull is the safety. DA/SA, first shot is double action ala revolver subsequent shots are single action 1911 style lighter trigger pull, decocker returns the hammer to a lowered "safe" position. The safe being a heavy trigger pull like a double action. There are variations on all these and many have combinations of manual and automatic safety systems unique to each weapon.