Sedimentary rocks are formed through the weathering and erosion of pre-existing rocks, transport of sediment, and cementation. Weathering breaks rocks into fragments, erosion transports the fragments, and burial/compaction under pressure binds the fragments together into sedimentary rock. There are three main types of sedimentary rocks - clastic rocks formed from fragments, bioclastic rocks formed from living organisms, and chemical rocks formed from mineral precipitation. Key features include fossils, ripple marks, and mud cracks.