You won't be surprised to learn that the skateboard was invented by a surfer who wanted to "surf" during the winter. During the winter months, it was naturally too cold to go into the water, so a solution had to be found that didn't involve going into the water. Eventually, this led to the creation of the longboard! The longboard has soft and large wheels, making it roll well and very suitable for moving yourself from A to B. The soft wheels also allow you to ride over irregularities (such as loose pebbles) without losing control of the board.
A skateboard, unlike the longboard, is very suitable for performing stunts and tricks. The hard and small wheels are very durable and ensure that you stand lower to the ground than on a longboard. The rigid frame of the skateboard ensures that you are able to make a stable landing and maintain grip on the board. The rigid frame also makes steering not so easy, so you mainly ride straight ahead.
A cruiser, in terms of functionality, sits exactly between a skateboard and a longboard. This means that you can transport yourself from A to B with the cruiser, but you can also do fun tricks with it. In terms of appearance, the cruiser looks very different from the two previously mentioned boards; the cruiser is small (usually between 55cm and 75cm) and has soft and wide wheels.