Sunblock and Sunscreen are the same thing to me, but I always say sunscreen. Suntan lotions are like the oily spray made to help you tan, like Panama Jack or something.
They are all separate products. The definition of sunblock vs. sunscreen is trickier and I only found out about it recently from the Lucie's List newsletter. Sunblocks create a physical barrier between skin and the sun, sunscreens use chemicals to absorb UV rays:
Re: CPW: What do you call...