The document discusses sedimentary rock, which forms from the compaction and cementation of sediments like sand, mud, and gravel over time. Layers of different sediments settle out of water or wind, with heavier particles sinking to the bottom over lighter ones. As additional layers accumulate through geological processes, the pressure and minerals binding them together transform the layered sediments into solid sedimentary rock. Common types include sandstone, limestone, shale, and conglomerate.