What kind of different focusing motors exist?

[jurat]

Sigma has USM and HSM. What does Tamron have? Or Nikon? What's the difference?

 

[jomike]

Sigma has USM and HSM. What does Tamron have? Or Nikon? What's the difference?

USM stands for Ultra Sonic Motor and HSM stands for Hyper Sonic Motor which is about the same thing. Nikon's equivalent is AF/S, the S stands for Silent wave motor.

Some focus motors in cheaper lenses are not USM/HSM and focus with these is noisier and slower.