Protein is constructed from amino acids. Proteins are made up of long chains of amino acids. Your body contains thousands of different proteins, each of which serves an important purpose. Each protein has its own amino acid sequence. The sequence causes the protein to take various shapes and perform various functions in your body.
Consider amino acids to be letters of the alphabet. Different words are formed by combining letters in various ways. The same is true for amino acids: different proteins are formed when they are combined in various ways.