A group of performers is a troupe. Any other group of people, military or otherwise, is a troop. A police officer, member of a mounted military group or similar person is a trooper, but a gung-ho worker is a real trouper.
Troops are always groups, despite the current vogue among journalists of saying things like “two troops were wounded in the battle” when they mean “two soldiers.” “Two troops” would be two groups of soldiers, not two individuals.
List of errors