A strut is a suspension-locating component, that controls movement of a component along the strut's length. It is typically implemented as a piston, that is designed with sufficient strength to withstand the twisting forces imparted on the end of the piston (that attaches to the hub).

As such, its function is typically combined with others: shock absorbers that are used as struts (i.e., the shock absorber IS the strut) are heavily fortified to resist twisting forces. A spring is also typically integrated into this component, as in a Macpherson strut.

One advantage of the strut design is that the suspension location points on the chassis are located relatively far apart, which results in lower stresses at those points, and hence the opportunity to use relatively softer bushings. A Macpherson strut also presents a compact package, especially for front-wheel-drive cars. One disadvantage of the strut design is limited camber control, since the hub is forced to travel along the length of the strut.

As an aside, the Benz front struts on a 201 do not have integrated springs. On a BMW Macpherson strut, the (integrated) springs are offset from the center to counteract the twisting forces imparted by the hub, which would normally cause "stiction" on the strut.