You can see that there are layers of different colors. At one time this whole area was under water. Streams brought silt and clay into the still water where it settled in layers as the years went by. Layers are laid down as the seasons change. Wet seasons carry more sediment than dry ones, so the result is a layered effect, like a pile of papers.
Some layers are very thin, some are thick.
Sometimes changes in the colors of the layers are caused by the streams bringing in a different kind of sediment. Geologists can someimes find traces of ash from large volcanic eruptions in the rocks. Sedimentary rocks preserve information from the distant past for us. Sometimes they contain fossils. Fossils are the remains of animals and plants that lived on earth many millions of years ago.