Electric guns are battery-powered and use a gearbox to compress a spring that when released shoots the BB out of the barrel. AEG's are normally powered by a rechargeable battery that works the inner mechanism. These guns usually obtain an fps, or feet per second, of about 200-450. They normally have a selector device that can achieve semi-automatic, 3-round burst, or full-automatic. Over the past few years, the AEG market has been swamped by many different cheaper-quality guns that may only reach about 200 fps at most. The three most common models of electric guns are M4/M16 series, G36 series, SCAR/MK. 16 series, and most recently, the FN2000 series. Arguably two of the best makers of AEG's are the Tokyo Marui and Classic Army brands. Both of the companies make state-of-the-art realistic AEG's that fire well. Most of the batteries used in AEG's are "stick" batteries that can fit easily inside the guns. Most batteries only last a few hours of continous fire, so if you are entering a competition, you will need lots of different ones. I hope this post has been helpful to anyone considering an AEG.