Amino acids are exactly what they say they are! They are compounds containing an amino group, -NH2, and a carboxylic acid group, -COOH. The biologically important amino acids have the amino group attached to the carbon atom next door to the -COOH group. They are known as 2-amino acids and are also known as alpha-amino acids.
Thumbnail: 3D model of L-tryptophan. (Public Domain; Benjah-bmm27).