Below is an exploded parts diagram of a prototype motor that I am in the process of designing and building. Let's clear up some of the vocabulary and nomenclature immediately. The can (or casing) hold a circular arrangement of magnets (electrically called poles) and is supported on one or both ends by endcaps. This whole rotating assembly is the rotor. Internally, the stator is a specially shaped piece of laminated iron pieces (the stack) which holds windings (or coils) made of turns of magnet wire on its projections (teeth). It is stiffly mounted to the shaft (a nonrotating axle) which also seats the bearings for the rotor assembly....
BLDC motors lie in the Awkward Gray Zone between DC motor and AC motors. There is substantial disagreement in the EE and motor engineering community about how a machine which relies on three phase alternating current can be called a DC motor. The differentiating factor for me personally is:
In a brushless DC motor, electronic switches replace the mechanical brush-and-copper switch that route current to the correct windings at the correct time to generate a rotating magnetic field. The only duty of the electronics is to emulate the commutator as if the machine were a DC motor. No attempt is made to use AC motor control methods to compensate for the AC characteristics of the machine...
I will admit that I do not have in depth knowledge of BLDC or AC machines. In another daring act of outsourcing, I will encourage you to peruse James Mevey's Incredible 350-something-page Thesis about Anything and Everything you Ever Wanted to Know about Brushless Motors Ever. Like, Seriously Ever.
http://krex.k-state.edu/dspace/bitstream/2097/1507/1/JamesMevey2009.pdf
There's a lot of things you don't need to know in that, though, such as how field-oriented control works. What is extremely helpful in understand BLDC motors is the derivation of their torque characteristics from pages 37 to 46. The short rundown of how things work in a BLDC motor is that an electronic controller sends current through two out of three phases of the motor in an order that generates a rotating magnetic field, a really trippy-ass thing that looks like this.
