Quadcopters like the one that crashed at the White House on Monday are among the most popular remote-controlled aircraft being sold today. But are they drones or sophisticated toys?

Sometimes it's very hard to distinguish between the two. It really depends on the particular model.

The devices are called quadcopters because they have four arms with propellers attached. Most weigh 2 to 5 pounds and are about 1 to 2 feet across. Their battery life is typically 15 to 20 minutes, and they generally are capable of flying only a few hundred feet in altitude. Many are capable of carrying cameras and perhaps very small packages, but not much more.

To carry a heavier payload, the aircraft typically must have more arms with more propellers. Octocopters with eight arms and propellers are popular small drones that can usually carry a heavier load than a quadcopter. A common, 9-pound octocopter has a liftoff weight of 22 pounds.

Some quadcopters are marketed as toys and sell for little as $40, but more capable models that can be equipped with cameras and other devices frequently sell for hundreds of dollars. They are being widely used for aerial photography and crop monitoring despite an FAA ban on most commercial drone use.

Reliability remains a problem. Nicholas Roy, a Massachusetts Institute of Technology professor, told a congressional hearing late last year that the reliability of most small drones is comparable to toys.