What is a biomass plantation?

This is an area that is planted with trees - often Willow or crops that will later be used as fuel.

According to Wikipedia "As a renewable energy source, biomass can either be used directly via combustion to produce heat, or indirectly after converting it to various forms of biofuel. Conversion of biomass to biofuel can be achieved by different methods which are broadly classified into: thermal, chemical, and biochemical methods.