I'll just add that camber isn't aerofoil thickness, it's aerofoil asymmetry.
An aerofoil with zero camber gives zero lift at zero angle of attack.
But a wing with camber can generate lift at zero angle of attack. This is important, because if the whole plane flies with an angle of attack then the body will be producing lift as well, and body lift is very draggy. You want to minimise the angle attack of the plane body.
But sometimes you do want to fly with high angle of attack - e.g. on landing. Adding additional camber with flaps can make the wing more resistant to stalling at high angle of attacks.