There are two main types of amino acids mainly talked about throughout bodybuilding, fitness and athlete performance fields, Essential Amino Acids(EAA) and Non-Essential Amino Acids (NEAA). There are 9 EAA and 11 NEAA, the difference between the two is EAA are needed by the body and cannot be produce by the body, however EAA can assist in the production of the other 11 NEAA, which means NEAA can be produce by the body. The 9 EAA are; Valine, Isoleucine, Methionine, Tryptophan, Phenylalanine, Lysine, Leucine, Threonine and Histidine. Essential Amino Acids can be absorbed through the food that we eat, and can commonly be found in protein rich foods such as fish, dairy, meat, rice, legumes, rice, peas, grains and can be absorbed through amino acid supplements.
The more you workout and become active the more demand is put on your body for amino acids to aid in repairing, maintaining and building of muscle. Meeting this demand can help your body to stay in an anabolic (muscle building) state. If the body doesn't get the required amino acid intake the body can turn into a catabolic state, in which the body may consume its own muscle fibers to gather the required amino acids needed for other bodily functions.
Amino Acid Blends are commonly formulated to aid in performance, recovery and building of muscle. The blends are often considered as intra-workouts(taken during a workout), post-workout(taken after a workout) or general blend of a range of amino acids. Blends that don't contain just amino acids commonly contain other minerals, vitamins and/or other energy ingredients and can commonly be taken throughout the day.