1) I guess it's only purpose is to make a photo in a shade of a specific colour. A blue filter for example will give the picture colder colours.
2) A polarizer filter reduces the amount of light flare against reflective materials ie. chrome. Also the colours are more saturated. For example, when I take pictures of a monument whilst kneeling and the camera pointing to the sky, the monument will have nice colours yet the background will be totally white. With the filter, the sky will have it's natural colours.
3) Ask TT
I'm not an expert on photography so somebody correct me if I'm wrong. Hope that helps.