A man with a toned chest has volume (bust) that is tight and perfectly smooth when relaxed or flexed. It looks "perky". A toned chest is also supposed to reveal the striations, or muscle fibers when flexed as this indicates minimal fat.
A man with fatty pecs tends to sag and isn't as hard because the pectoral muscles are too fat and not enough muscle mass to really create that definition.
I've seen man boobs that actually look like boobs. Whereas a strong chest will be well built all over the chest, and the guy will probably have muscly arms too as opposed to flab. His chest will be tense and strong looking and feeling, not flabby.
One is fleshy and flabby, the other one is hard and muscle.