Litter consists of waste products that have been disposed improperly, without consent, at an inappropriate location. Litter can also be used as a verb. To litter means to throw (often man-made) objects onto the ground and leave them indefinitely or for others to dispose of as opposed to disposing of them properly.
Larger hazardous items such as tires, appliances, electronics and large industrial containers are often dumped in isolated locations, such as National Forests and other public land.
It is a human impact on the environment and is a serious environmental issue in many countries. Litter can exist in the environment for long periods of time before degrading and be transported large distances into the world’s oceans. Litter can affect quality of life.
Cigarette butts are the most littered item in the world, with 4.5 trillion discarded annually. Estimates on the required time for cigarette butts to break down vary. They range from five years to 400 years for complete degradation. 
(From Wikipedia , June 2015)