What is the difference between sunscreen and sunblock?

Sunscreen/sunblock: The difference between is how good they are at screening out harmful radiation from the sun. Blocks are stronger and thus more effective at keeping out those harmful UV rays. Blocks are also usually more visible. For instance, the white zinc oxide life guards use on their nose is more of a block. Nothing is 100% though, so hats with wide brims and lightweight clothing works well too!