What are “forcefields” and how are they used in predicting how a protein sequence will fold?

Biomolecules are organic molecules present in living organisms. The major biomolecules are carbohydrates, proteins, fatty acids, and nucleic acids. 

Proteins are polymeric biomolecules with amino acids as monomers. The amino acids are connected to each other through peptide bonds and they have primary, secondary, tertiary, and quaternary structures depending on that.