The motor from a 3.5″ floppy disk drive. The coils, arranged radially, are made from copper wire coated with blue insulation. The well balanced rotor (upper right) has been removed and switched upside-down. The grey ring inside its cup is a long term magnet.
A brushless DC electric motor (BLDC motor or BL motor), also called electronically commutated motor (ECM or EC electric motor) and synchronous DC motors, are synchronous motors powered by DC electrical power via an inverter or switching power supply which produces an AC electric current to drive each phase of the motor via a closed loop controller. The controller provides pulses of current to the engine windings that control the acceleration and torque of the motor.
The construction of a brushless motor system is normally similar to a long lasting magnet synchronous engine (PMSM), but may also be a switched reluctance electric motor, or an induction (asynchronous) motor.[1]
The advantages of a brushless electric motor over brushed motors are high power to weight ratio, high speed, electronic control, and lower maintenance. Brushless motors discover applications in such places as computer peripherals (disk drives, printers), hand-held power tools, and vehicles ranging from model aircraft to automobiles.
In a typical DC engine, there are long term magnets externally and a spinning armature on the inside. The long lasting magnets are stationary, therefore they are known as the stator. The armature rotates, so that it is called the rotor.
The armature contains an electromagnet. When you run electrical power into this electromagnet, it generates a Leaf Chain magnetic field in the armature that 
draws in and repels the magnets in the stator. So the armature spins through 180 degrees. To keep it spinning, you need to alter the poles of the electromagnet. The brushes manage this modify in polarity. They make contact with two spinning electrodes attached to the armature and flip the magnetic polarity of the electromagnet since it spins.
his setup works and is easy and cheap to manufacture, but it has a lot of problems:
The brushes eventually wear out.
As the brushes are making/breaking connections, you get sparking and electrical noi
The brushes limit the maximum speed of the motor.
Having the electromagnet in the heart of the motor makes it harder to cool.
The use of brushes puts a limit on how many poles the armature can have.
With the advent of cheap computers and power transistors, it became possible to “turn the engine inside out” and get rid of the brushes. In a brushless DC electric motor (BLDC), you put the long lasting magnets on the rotor and you move the electromagnets to the stator. You then use a computer (linked to high-power transistors) to charge up the electromagnets as the shaft turns. This technique has a variety of advantages:
Because a computer regulates the motor rather than mechanical brushes, it’s more precise. The computer may also factor the acceleration of the motor in to the equation. This makes brushless motors more efficient.
There is no sparking and far less electrical noise.
There are no brushes to degrade.
With the electromagnets on the stator, they are very easy to cool.
You can have a lot of electromagnets on the stator for more precise control.
The only disadvantage of a brushless engine is its higher initial cost, but you can often recover that cost through the higher efficiency over the life span of the motor.