NEMA 5-15 and 5-20 are the ones you'll use most.

Yes, but the specific one depends on what you’re plugging in.

For heavy-duty extension cords around the house or job site, NEMA 5-15 is the standard three-prong plug (two vertical blades plus round ground). That handles 15 amps at 125 volts—most tools, shop vacs, and holiday lights.

If you need more power, like for a compressor or table saw that draws 20 amps, you want a NEMA 5-20 plug. It looks like a 5-15 but with one blade turned sideways (T-shaped neutral). Won’t fit a standard 15-amp outlet