This is one of a series of "RC Basics" videos for those who are new to the hobby.
Although most existing RC fliers probably already know all the information presented in this video, there are many newbies who don't - so I'm providing this occasional series for the complete beginner and assuming no prior knowledge.
This video looks at the humble brushless electric motor and shows the difference between inrunners and outrunners, as well as how the numbers sometimes define the size of the motors.