​​What is purpose of Filter in Cigarettes ?

A cigarette filter has the purpose of reducing the amount of smoke, tar, and fine particles inhaled during the combustion of a cigarette. 
Filters also reduce the harshness of the smoke.
Most cigarette filters are made of the same material as camera film (cellulose acetate). Each individual filter is made of thousands of tiny fibers. The inside of the filter is painted white to make it appear clean. During smoking, these fibers can come off into your mouth and be inhaled into your lungs.