What do the items like exp share and exp all do?

Exp Share will give half the experience points to the Pokemon holding it in battle when it doesn't have to fight.
Exp All is the same, but divides it up between all your party Pokemon.

Thanks what about exp. lock?

Exp. lock will not let your pokemon gain exp. I think that's the purpose of it.

Wow messed up item thanks

Exp lock's purpose is to keep base pokemon at their base level if you accidentally earned any experience for your roster. I used it in my arceus so he will remain at his base :)