Immunoelectrophoresis is a technique that combines electrophoresis and immunodiffusion to separate and characterize proteins. It involves applying an electric current to separate antigen mixtures placed in agar gel wells. Antibodies are then placed in troughs cut parallel to allow diffusion. Precipitation lines form where antibodies interact with specific antigens, allowing visualization and identification of different protein components in the original sample. Immunoelectrophoresis is useful for analyzing serum proteins and detecting monoclonal gammopathies, but is slower and less sensitive than related techniques like immunofixation electrophoresis.