Work is done when a force causes displacement in the direction of that force; it is the product of the force/displacement and the component of displacement/force in the direction of that force. When done on an object, the object is given energy. Having energy means having the ability to do work.
W = F[sub]x[/sub]Δx or F[sub]y[/sub]Δy
the force and displacement must be parallel
It is a SCALAR quantity
While work can be negative, the negative sign does not refer to direction. Rather, the negative work indicates that energy was lost. Positive work indicates an energy gain.