RE: compound?
A compound movement typically refers to a movement that involves more than one muscle group. Classic examples would be chest presses (chest, front delts, tris all involved) or squats (glutes, quads, hams all involved.)
Shoulder presses would use shoulders, tris, and perhaps some upper chest and traps too depending on your positioning.
A compound movement is contrasted with an isolation movement that only involves 1 muscle group. An example might be a bicep curl which only involves the biceps, or a leg extension for just the quads.
That said, I am not sure that there are any truly isolation movements. For example I think the bicep curl would involve some forearm. I also think the traps get worked a bit with front raises for the shoulders. But I think that on these movements the secondary muscle involvement is much less than with the "compound" movements.
Someone with more education than me (self taught by books and mags) can jump in here at any time. No insults taken.
You may have been thinking of a compound SET.
Hope this helps. Jeanne