The one on the left is not a bullet. 
But its main use is for internal stimulation, with the added bonus of also being able to use it on your clitoris too if you want to.
There’s an A-Z of Sex Toys that you might find fun. 
Edit: Actually, I think a better one would be the Beginner’s Guide to Vibrators. I thought the A-Z was a glossary, but I think they’ve changed it.
Edit Edit: And here’s a copy of the original A-Z I was thinking of (turned into a forum wiki ) - Sex Toy Glossary - wiki draft