http://i1277.photobucket.com/albums/...psb6138ce4.jpg

a mob dropped what is this thing

Do you already have 7 dragonballs in your inventory? If so that is a dragonball. If you have all 7 in your inventory and you kill a DB mob and they drop a ball you can only pick these up, only after using your dragonballs can you start to get normal dragonballs again.
If not it is just a crafting item.

Also instead of making a new thread, post here http://dbocom.com/forum/showthread.php?t=6139 if you wanna know what items are.

so what is this and how can i use it

It is a crafting item afaik. Either you can try selling it or throw it. That is what i usually do.