What are the differences between a cassette and a freewheel in BMX bikes?

In BMX bikes, a cassette and a freewheel are both types of rear hubs that allow the rider to coast without pedaling. The main difference is that a cassette has multiple cogs (gears) that are integrated into the hub, while a freewheel has the cogs attached to a single unit that screws onto the hub. Cassettes are generally more durable and allow for smoother gear changes, while freewheels are easier to replace and maintain.