The Short Answer
An undermount sink is mounted below the countertop edge — the countertop material overlaps the top rim of the sink, creating a clean edge with no visible rim. An apron-front (farmhouse) sink has a large exposed front panel that replaces the cabinet face frame. Undermount sinks are compatible with any base cabinet and can be installed in new or existing kitchens without cabinet modification. Apron-front sinks require a modified or purpose-built base cabinet. Undermount requires a solid countertop material (quartz, granite, stone) — it cannot be used with laminate. Apron-front can be used with any countertop material.