what does 4WS (four wheel steer) mean what does it actually do and how comes a car having four wheel drive adds more weight than the same car having 2 wheel drive anyone any answers

If you'd just typed your questions in google you'd have got answers. That said.

Q1) Four wheel steering is a system used by vehicles to improve stability when moving at high speed (turning/changing lane, etc) and also at times to decrease turning radius at low speed.

London Taxis famously use it and it helps reduce their turning circles so that they can take very sharp corners into narrow London streets.

These 4 wheel steering systems steer as you might guess the rear wheels as well, though in most systems they don't turn as much as the front and all of the wheels are controlled by one single steering wheel (the rears know just how to turn thanks to computers/actuators).

Not many vehicles have 4 wheel steering.

Q2) Four wheel drive means the engines power is provided to all of the wheels instead of just to the front or rear two. Four wheel drive systems add weight because they require extra components between the front and rear wheels. Many 4 wheel drive systems allow a balance between front and rear depending on what the conditions are, i.e. if increased grip is needed power is divided evenly. If your just driving on the road, power is given largely or entirely to the front wheels to save fuel. To do this large heavy clutches and slip diffs are needed. All of which add weight.