The DNA rearrangements that is responsible for the diversity of the lymphocyte receptor specificity and idiotypic antigenicity produced by the V, D, and J DNA segments.
Always forgetting which is which? Here's a mnemonic
VDJ = more genes = Bigger (heavy) chain of the immunoglobuline variable redgion and Beta chain of the TCR
VJ = less genes = light chain of the immunoglobuline = alpha chain of the TCR
Hope that helps