Skateboard is what most street, vert, pool skaters ride because of it's concave (curved structure and with the nose and tail pointing upward), it allows skaters to pull out tricks such as kickflip by kicking on a certain point which makes the board flip. A longboard, on the other hand, is not meant to be used for kickflip or ollies because of a lack of concave and tail/nose. A longboard often is used as a way to get around because of how much control you get out of it due to more areas of your feet is on the board.
Many people misunderstood that skateboards are for trick and longboard is just a way to get around. A longboard is more than that. A longboard can also use to do tricks, just in a different way. Some examples of longboard tricks would be Cross-Stepping, The Shanker, Spin big and many more! So please don't think a longboard can't do tricks. I have also seen someone skate in FDR skate park in Philadelphia with a longboard.
I personally skate street, so I use a skateboard. Also, there are different types of longboards, some are designed for going downhill, some are designed for dancing (tricks on a longboard), some are designed to just cruise and do whatever you like, etc. But a longboard can absolutely do tricks, different but tricks in the full meaning of the word. Hmm, well enjoy skateboarding and keep rolling!