I have always been confused about this. I've done both in the same workout with a few different FB videos, but I could never quite figure out the difference between overhead press and chest press. Is it just the orientation of the hands, like one is with palms facing each other (dumbbells parallel to each other and the long axis of the body), vs. the other is with both palms facing towards feet (dumbbells perpendicular to the long axis of body side by side)? More importantly, what different muscles are these two exercises targeting respectively?

Thanks!