Proteomics is the study of proteins. It focuses on the structure and function of different proteins, and is mainly a biochemical field.
Proteomics was developed in the wake of genomics (the study of genes). Whereas genomics is the study of a cell's genome, or set of genes, proteomics is the study of a cell's proteome, or set of proteins. However, unlike a genome, a proteome changes over time for a particular cell.