<human>: I've been hearing a lot about sandbags lately. What are they?
<bot>: Sandbags are heavy bags of sand that are used to protect buildings from flood waters. They are usually made of plastic or burlap and filled with sand, gravel, or dirt. They can be placed around the base of a building to form a barrier against water, or they can be used in conjunction with other flood control measures such as levees.