Filters are used to change the properties of the light before it gets to the film or image sensor of your camera. Some may say with digital cameras you can always make the changes in PhotoShop, but why waste the time doing that when you can get the effects you want at the camera. With a film camera this is the way it is done...
Below is a list of some of the most popular filter used in photography.. Click on the link to get a description of what they are used for.