Steroids will increase the total muscle mass you can have as well as let you increase it faster. If you're on steriods and weigh 220, when you go off you'll lose a lot of that muscle mass. Steroids allow muscle mass that's not possible with just training.
Google is your frenemy.
Caveat Emptor - Latin for tough titty
I tend to interpret things in the way that's most hilarious to me