Positive work :
Positive work means that force (or its component) is parallel to displacement 0º ≤ θ < 90º
The positive work sigmnes that the external external force favours the motion of the body.
Negative work :
Negative work means that force (or its component) is opposite to displacement i.e., 90º < θ ≤ 180º
The negative work sigmnes that the force opposes the motion of the body.