It was about a dozen labels operated by one company. Tamla was the originial label, Motown as a label came second. Other labels included Soul, Gordy, etc.
I think, in the UK the label was issued initially as Oriole, then as $tateside (an EMI label), then as Tamla-Motown (also EMI).
I just checked and before Oriole, the UK issues were London American (a Decca label) and then Fontana (a Phillips label)