E-boats and R-boats serve different roles

What was the difference between an E-boat and an R-boat?

E-boats normally meant Schnellboote, while R-boat referred to German Räumboote, principally minesweepers that could also perform other tasks and varied widely in size.

Schnellboot is the vessel most commonly meant by E-boat in this context. R-boats were Räumboote intended principally for minesweeping, though they could carry guns, mines, depth charges, or even torpedoes for other duties. Their displacement varied considerably across different classes. Captured French, Dutch, British, and other vessels further complicated the category, so the specific flotilla and hull matter more than the label alone.