a compund exercise is something like a squat, deadlift, good morning, bench, etc... it works out MORE than one muscle group hence the name compund
isolation exercise just works out ONE muscle group. like bicep curls, tricep extensions etc.
Each have their place in lifting but compound lifts are far more beneficial to muscle building than isolation exercises. And thats not to say isolation exercises dont have their place in training, but keep them to a minimum and have most of your training compound exercises
