Quickly understand the relationships between amino acids, peptides and proteins

We all know that amino acids are the basic building blocks of proteins. So what's a peptide, what's an oligopeptide, what's a polypeptide?

A peptide is a polymer formed by covalently linking two or more amino acids through peptide bonds, a compound in which amino acids are linked by peptide bonds, and the product of incomplete protein hydrolysis is also a peptide. Peptides are called dipeptides, tripeptides and tetraceptides according to the number of amino acids they consist of. Generally, oligopeptide consists of less than 10 amino acids, while polypeptide consists of more than 10 amino acids.