Sedimentary rocks.

Sedimentary rocks form at the Earth's surface, not from heat like igneous rock, but from the slow accumulation and compression of material over time. There are three ways this happens, and they produce genuinely different-looking rock:

Clastic sedimentary rocks form from broken fragments of other rocks — sand, silt, gravel — that get deposited (usually by water), buried, and compacted together, often with minerals crystallizing between the grains to cement them into solid rock. Sandstone is the classic example.

Chemical/biochemical sedimentary rocks form when minerals dissolved in water precipitate out and accumulate — sometimes with the help of living organisms building shells and skeletons out of those minerals. Limestone is the big one here.

Organic sedimentary rocks form from compressed plant or organic material. Coal is the main example.

The thing that ties all sedimentary rock together, regardless of which path it took: it usually forms in layers, called strata, since material deposits over time in successive sheets. That layered look is often the fastest way to recognize a sedimentary rock in the field.