What are rock ensembles?

I went searching around the net to find out and all i came up with was the names of some really good rock bands. I'll try find out something useful but it might take a while =(

An "ensemble" is a small group of musicians playing the same piece of music. Therefore, "rock band" is a perfect synonym for "rock ensemble."

=)

And, if you had not entitled this question music, a rock ensemble could have been a collection of gemstones.

:)

Thanks. :)