Polarizing filters reduce glare and increase saturation levels, while UV (ultraviolet) filters protect your lens and reduce haze in film cameras. The best type of filter depends on your camera and what type of pictures you take.
Polarizing filters reduce reflected light, which makes skies a richer blue, reduces glare on water and increases the saturation of the image. However, polarizing filters make some landscapes look unrealistic and also increase the likelihood of a blurred shot.
UV filters prevent UV light from reaching the film or the digital camera sensor. UV filters improve the clarity of film photography, but they do not improve and may even detract from digital quality. UV filters also protect the front of a camera lens from damage.
If you use a film camera or if you want to protect your digital camera, use a UV filter. If you use a digital camera and often shoot landscapes or other outdoor shots, a polarizing filter is your best choice.