supersets

Supersets are where you pair two exercises and complete them back to back, almost in a circuit.

So if it was chest day, one superset could be
A1 Chest fly
A2 Push ups

And you repeat the exercises for the number of sets you're doing and the number of reps e.g. 3 x8 for each would mean you would do A1 8 times followed by A2 8 times and then repeat x3.

However, I'm no expert but I think I'm right in saying usually they say to superset opposing muscle groups or opposing motions i.e. like a push and a pull.

I usually alternate muscle groups for supersets. So if it's chest and tris day I could do the chest fly then dips.