In general, there are two kinds of waves:
For transverse waves, the individual disturbance is perpendicular to the direction of the wave motion as a whole.
A wave on a string is a transverse wave. Light is a transverse wave.
Sound is a longitudinal wave. A slinky toy can support a longitudinal wave.
Longitudinal waves can not be polarized. Light is a transverse wave so it may be polarized.
(C) 2003, Doug Davis; all rights reserved