For whatever reason, slip seems to confuse folk.
Slip = the breeze is coming from a direction laterally somewhat off the nose. For zero slip, the wind is head on to the aircraft.
Sidesliip = slip ie terminology only
forward slip = Americanism for slip when the intention is to maintain a desired track generally with respect to a ground feature, eg runway
crab angle = angle betwixt heading and track - need have no slip and generally doesn't.