Bio mass:\tPlant and animal wastes (dung), vegetable wastes, sewage are decomposed in absence of oxygen to produce Biogas\tSince the source of these fuels is animal dung, the source of these fuels is called Biomass.\tIt is commonly called Gobar-gasHydro power:\tDams are constructed at heights to obstruct the flow of water and store it. The stored water has Potential Energy.\tWater stored in heights now is allowed to flow to low levels. The potential energy is converted to kinetic energy and moves the turbines. Electricity is produced.\tThis is called Hydroelectricity because the potential energy of water which is stored at elevated heights is converted into kinetic energy of flowing water which in turn is converted electricity\tIt is a renewable source of energy, since rainfall comes over and over again.