Hi Kathy -
I'm not sure but I think the difference between the two types of workouts is one is for strength (Cathe) and the other for endurance (Joyce).
There was a recent post about this. Strength - for example - would be picking up your child. Endurance - would be holding your child for a half hour. Also there was some mention in that same thread about how each one employs either the slow twitch or fast twitch muscles. Not sure which is which.
As I look back and read this, I can tell that I'm not being much help but I'm trying!