A conglomerate is a coarse-grained clastic sedimentary rock composed of rounded gravel, pebbles, cobbles, or boulders (particles >2 mm) cemented in a finer matrix. The key distinguishing feature is rounded clasts, indicating significant transport before deposition. Breccia is similar but contains angular clasts, implying short transport distances. Both belong to the rudaceous (psephitic) sedimentary classification.