These are DC motors that have permanent magnets on their stators instead of field coils. Functionality is retained but the motors are simpler and more compact. Large, powerful motors are very difficult to construct mainly because of the difficulties in fabricating big permanent magnets. Neodymium magnets allowed the building of very small and powerful motors, but these magnets are costly and prone to cracking under mechanical stress. As a result, permanent magnet motors are usually confined to low-power tasks, where simplicity and small size are paramount such as toys, battery-powered tools like screwdrivers, etc.
Another disadvantage is the fact that, in spite of their name, all permanent magnets lose strength over time. Field coils do not have this issue as they produce the magnetic field on the spot.