What's the difference between a goblin and a hobgoblin?

The main difference between goblins and hobgoblins is that hobgoblins think that they are funny.
https://www.quora.com/Mythical-Creatures-Is-there-a-discernible-difference-between-a-goblin-and-a-hobgoblin

They look different also.

http://www.hub-uk.com/images012/hobgoblin02.jpg

http://astarlite.com/heathfieldcastle/GoblinBW.jpg

Hobgoblins are a sort of rougher brownie, with more of sense of humour (which may not always be to the householder's taste). Like brownies, they do odd jobs round the house. Goblins, on the other hand don't work for you. They vary from just being a decided nuisance to being outright evil. Both can be about the same size. The two terms have been confused in more modern times, with some thinking that a hobgoblin must be worse than a goblin. The 'hob' bit is a form of 'Rob' as in Robin Goodfellow.
https://en.wikipedia.org/wiki/Goblin
https://en.wikipedia.org/wiki/Hobgoblin