This article is from the Radio Control (R/C) Flying FAQ, by Shamim Mohamed email@example.com with numerous contributions by others.
The power system includes a battery, a motor, a control, and wiring. The
battery is almost always made up of Sanyo NiCd cells in the appropriate
number. Motors vary from the simple, cheap "can" type (otherwise known as
"540" or "550" style), through more sophisticated styles adapted from RC
car motors, up to the cobalt powerhouses.
Controls can be a simple on-off switch controlled by a servo, a directly
controlled on-off switch, or a proportional electronic control.
If you are going to fly a glider or old-timer type plane with less than a
500-watt motor, think seriously about getting battery packs made of Sanyo
900 SCR cells. They are significantly lighter than the more usual 1200 mAH
(sub-C) cells and give excellent performance.