BTW, if anyone wants to learn about 2-way and 3-way switches online, don't. There is no subject I have ever seen as horribly fouled up online. If you do a Google search on the subject, you will get many, many, many pages of links with incorrect info in them.
Here's the correct info:
1-way switch: No such thing.
Single pole switch: This is the standard switch that controls a device from 1 location. Up is on, down is off. This is sometimes incorrectly called a 2-way switch, or a double pole switch.
Double pole switch: This is a single switch that can control 2 circuits at the same time. Very rare. You won't find them at Home Depot.
2-way switch: This is actually an industrial switch with the ability to power 2 different devices, but NOT at the same time. Picture a rocker switch. 3 positions- up powers one device, down powers another. Center position both devices are off.
3-way switch: This is a switch that can work in conjunction with another 3-way switch to power devices from 2 locations. Either switch has the ability to cut the flow of current. This is sometimes incorrectly called a 2-way switch.
4-way switch: This is a switch that can work in conjunction with (2) 3-way switches to power a device from 3 or more locations. This is sometimes incorrectly called a 3-way switch (although (2) 3-way switches are necessary to make a 4-way switch work at 3 locations)
It's easy! Just remember... If the device is powered from 1 location, its a single pole. If it is powered from 2 locations, its a 3-way. Double-pole or two way switches probably don't exist in your home. If it is powered from 3 locations its a 4-way (plus (2) 3-ways). If it is powered from 4 locations, its (2) 4-ways + (2) 3-ways. If it is powered from 5 or more locations, its (2) 3-ways + a bunch of 4-ways. Simple, right? HaHaHa!!
It's almost as good as trying to learn the English language! 
