What is the difference between mainstream smoke and sidestream smoke?

What is mainstream smoke?

 A smoker that inhales the smoke and exhales the smoke into the environment is called mainstream smoke. 

What is sidestream smoke?

Smoke that is released into the environment from a burning cigarette is called sidestream smoke. 

What is the difference?

The difference between the both is that mainstream smoke is a smoker that inhales the smoke and exhales the smoke into the environment and sidestream smoke is Smoke that is released into the environment from a burning cigarette.