Monomers are building blocks of polymers.
Monomers are identical repeating units which bond covalently to form polymers.
Consider a pearl necklace with identical pearls here the necklace is the polymer and the pearls are monomer units each pearl is bonded to one monomer on its right and one monomer on its left.
So essentially monomers can bond with at least two other monomer molecules.
Polymerization is the process of formation of polymers.
Considering they are polymers made of repeating units of amino acids so here amino acids are the building blocks(monomers)