ORIGINAL: wake wacker J

To make the motor turn you need opposing charges. The magnets charge is fixed and the opposing charge comes from current through the coil which is wound onto the armature. This opposite charge pushes away on each other causing the armature to spin.

On a brushed motor the coil is wound onto the armature (the part that spins). These motors need a way to get the current to the coil which is spinning so there are brushes that ride on contacts (commutator) that give current to the coils.

On a brushless motor the coil or windings are on the inside of the can and don't move. The fixed charge magnets are on the armature. You don't need brushes because you can directly hook wire up to the coils because they don't move. In a brushless motor it is the magnets on the part that spins so electrical contact to the armature is not needed. Hence, no brushes on a commutator to cause drag so up goes the power and efficiency. Another nice thing about the brushless is that water cooling will have more effect because the coils are what you want to cool and since they are on the can...they can be cooled well.