BCAAs (Branched Chain Amino Acids) are essential Amino Acids which are required for maintaining lean muscles mass. L-Leucine , L-Valine and L-Isoleucine are collectively known as BCAAs.These are essential Amino Acids and these Amino Acids cannot be synthesized in human body. Therefore you need to include enough quantity of these Amino Acids in your diet or it can be taken as supplement.