Primary structure of a protein refers to the linear sequence of aminoacids in the polypeptide chains.
Secondary structure is the pattern of H2 bonds of the protein that are observed in the atomic resolution structure.
Tertiary structure will have a single polypeptide chain "backbone" with one or more protein secondary structures. Amino acid side chains may interact and bond in a number of ways.
Quaternary structure is the number and arrangements of multiple folded protein sub units in a multi sub units complex