Strut comes from the term MacPherson(spelling?) Strut, which is a type of suspension that uses the damper as both a load bearing element of the suspension and a suspension locating element. (That sounds kinda weird, maybe someone else can better explain it)
A shock doesn't have to be a load bearing element or a suspension locating element, which is the case on the rear of a focus (it's not a coilover).
Q: What is the difference between shock absorbers and struts?
Struts and shocks are very similar in function, but very different in design. The job of both is to control excessive spring motion; however, struts are also a structural component of the suspension as they can take the place of two or three conventional suspension components.
In a strut suspension, the strut is actually one of the suspension links and plays a role in determining the suspension geometry.
If you have a double-wishbone setup, you have an upper control arm to determine changes in camber. Moving the strut does not change the wheel alignment because it is not a link of the suspension; alignment is now the task of the two control arms and can be optimized with a bit more control.
Because if the camber curves and more easily controlled roll center (the axis upon which the car rolls), double-wishbone suspensions are vastly superior to strut setups. Lower a strut suspension and you will lose dynamic camber, a bad thing. Drive an older Civic with the double-wishbones back-to-back with a newer Civic and you'll definately feel the inferiority of the newer model, blamed on its use of struts. Strut suspensions are used because they are compact (important in FWD) and cheap (less parts).
The modern "multilink" suspension is functionally similar to a double-wishbone suspension, however an extra link is added, typicaly to create a change in toe.