What is meant by tertiary structure of proteins?

Tertiary Structure of Proteins:When secondary proteins undergo a third degree of twisting or torsion formed by additional bonds of both functional groups; the proteins is then called tertiary structure of proteins. The polypeptide chain is twisted and folded to from a stable structure. It is maintained by three types of bonds i.e. ionic bonds, hydrogen bonds and disulphide bond e.g. Myoglobin protein shows a tertiary structure.