Protein sequences are the specific order of amino acids that make up a protein. Each protein is composed of a unique sequence that determines its structure and function. There are 20 different amino acids, and the sequence in which they are arranged is crucial for the protein's role in biological processes. The information about protein sequences is often represented using a string of letters, where each letter corresponds to a specific amino acid. Scientists study these sequences to understand how proteins work and how they interact with other molecules in living organisms, contributing to fields like biochemistry and molecular biology.