220-240v (they are all basically the same even though the appliance or tool may be rated at either end or in the middle as 230v) has 2 hots and a neutral. It's basically two circuits melded into a single line. There are a couple of different configurations for a 220 outlet, that's why they always sell the cord separate when you buy an electric dryer or stove, so you can buy the cord that works with the outlet. You can pull a single 20 or 15 amp line off a 220 but not the other way around - it's supposed to have a dedicated breaker. If the prongs on the compressor don't fit your outlet, it may be easier to find or have made an extension cord with the proper ends on either side - you may be able to find an extension that splits the line so you have a dedicated plug for the dryer and another for your compressor. If your compressor is to remain stationary, it's always better to add a dedicated circuit right to it, as rowhard suggests.

-- John