Whats the difference between Shocks and Struts?

Wheres a good site, another than E-bay to buy a complete Strut Bar kit?

 

They both control the up and down motion of the car, but struts are a standalone part of the suspension. Basically, if you take a shock off of a car, the axle will still be completely attached to the vehicle. If you take off a strut, the axle will be able to move outside of its usual position.

As for places to buy, eBay is the only website I use to shop for car parts, so I dunno.