WHAT DOES GREEN ENERGY WOOD PELLETS FOR HEATING MEAN?

I am leaning towards a pellet stove mainly because I by now burn off pellets in my basement. Also a woodstove would require a large amount of piping and would have to be Situated near the middle on the garage to vent out of the roof higher than the ridge. I'm planning on purchasing a utilised pellet stove hopefully all over forty,000 BTU's.Assembly