As powerful nucleophiles, enolates react readily with a variety of electrophiles. These reactions generate new C-C bonds and often new stereocenters. The stereoselectivity and regioselectivity is influenced by additives, solvent, counterions, etc. One important class of electrophiles are alkyl halides, and in this case a classic problem arises: O-alkylation vs C-alkylation.  Controlling this selectivity has drawn much attention.  The negative charge in enolates is concentrated on the oxygen, but that center is also highly solvated, which leads to C-alkylation.
Other important electrophiles are aldehydes/ketones and Michael acceptors.