Sedimentary rocks are formed when small fragments of other rocks or sediments settle and compact to form a brand new kind of rock. You can usually see layers within the rocks that are diferent types of materials.
There are also different types of ways for it to form, such as clastic, which is made of rock fragments. Another way is organic, which is when plant or animal remains are squished and turned into fossils. The last way is chemical which is made from disolved minerals after they evaporate. Sedimentary rocks are usually made up of quartz and calcite.
Just like igneous rocks, sedimentary rocks also have unique characteristics like fossils and sand. They are usually rough and hard, but not very strong and can break easily.