Paddles! Hooah! What are they good for?

So I have small paddles I use for *** drill (pressing the water). I've swam a little front crawl with them too but I don't really know what I ought to be doing. What is the use of paddles going to do for me? Are there various types of target goals (speed or sttrength) that require different uses? Will it create shoulder issues? Any set ideas for an average swimmer? Should I swim or just pull with them on? Thanks...