A cruiser skateboard is a specific type of board designed for cruising down streets, city environments, or basically any level pavement. Many cruiser boards have a kicktail, which is the part that curves up at the end on the back. That isn't always the case, though, and cruisers aren't specialized for doing tricks like skateboards are. They're also not designed for going fast or downhill.
Here are some key design aspects of a cruiser:
Medium or shorter deck length.
Kicktail in the back, sometimes.
Big, tough wheels compared to skateboards.
Easy to transport.
Shorter than longboards but with a similar purpose