I will further explain with a simple example If I had a dataset as follows:
Team Score
Blue 4
Blue 8
Green 8
Orange 7
Blue 4
Red 5
Red 4
Orange 10
Blue 3
Green 8
Green 5
I want do to something to get the means that expresses:
mean(Score[Team=Blue])
mean(Score[Team=Green])...
I want to be able to do it all at once.