It confused me at first, I couldn't understand why you would want to put "ocean water" in a pool! So I read up on the process, and it really should be described as a natural chlorine system. Salt is put into water (about 1/12 as much of a concentration as ocean water) and the solution of water and salt is sent through the chlorine generator. The salt used is common table salt but check with your pool builder to make sure nothing specific (i.e. with some modifier) is better, and is probably sold at a pool store.

In fresh water swimming pools salt is added to the water and evenly dispensed via the same machine (the chlorine generator) that produces the electricity. The low voltage electricity creates a chemical reaction that releases chlorine vapor which is instantly dissolved into the water. This low concentration keeps the water clean and sanitary, and doesn't sting the eyes and skin.

There are numerous benefits to using a salt water pool explained in the video linked below that I highly recommend you watch - it is short and to the point, and not too much chemistry!

Watch a video that explains a salt water pool.