Bone up/Bone up on ?

Hello everyone

Can you explain to me the meaning of bone up ?
And when can we use it ?
also what's the difference between bone up and bone up on ?

Also mug up and mug up on ?


Thanks alot

Bone up on - English Phrasal Verb - UsingEnglish.com
Mug up on - English Phrasal Verb - UsingEnglish.com