VDJ recombination is the mechanism by which B cells generate antibody diversity. It involves genetic recombination of variable (V), diversity (D), and joining (J) gene segments in B cell progenitors. This creates a unique B cell receptor on each mature B cell. The process occurs in two steps - first recombining the heavy chain loci, then the light chain loci, without a D segment. Key enzymes like RAG and TdT introduce randomness to generate the vast antibody repertoire essential for recognizing diverse pathogens.