http://www.rcuniverse.com/forum/rc-c...batteries.html
That'll get you started and explain the Lipo side pretty well. Brushless isn't all that different from brushed. There's still a motor and esc but the "turns" in a motor don't mean as much as they used to. Instead we use "kv" now, which is just a way of expressing how fast a motor will spin (unloaded) per volt that is applied. Example a 4000kv motor will spin 4000rpm when one volt is applied to it. There's more sizes of motor availible now too but there's still the familiar 540 and 550 can sizes especially in racing classes. Brushless is also more demanding on the batteries so going Lipo is almost a must. In some cases NiMh can actually hurt the esc due to ripple voltage.
Another big big difference is Sensored vs sensorless. Sensored motors have a sensor on them to tell the esc the position of the motor. Sensorless motors don't have a sensor and instead use EMF signals coming back through the motor wires to determine the motors position. Sensored has smoother startup and low speed drivability so it's the choice of crawlers and can be an advantage while racing. Most sanctioned race tracks require sensored in their professional and sanctioned races. It's possible to run sensored motors on sensorless esc's but the motor may not like it too much. Some esc's can run either sensored or sensorless while others cannot.