Sedimentary Rock
Sedimentary rock is made from sediment and, or by other chemical reactions. Sediment is loose material, that can include bits of rocks, minerals, plants, and animal remains. Water, wind, and ice can move sediment to a place where it can settle. Sedimentary rocks are usually formed in oceans and lakes were larger, heavier fragments settle first. Each layer of sediment is squeezed together by the weight above it. An example of sedimentary rock is sandstone shown in the picture to your right.
Cementation
Minerals in rocks dissolve as water soaks into them which can make them become smaller rocks as small as grains of sand if there is enough time. Also sand is actually rocks that have either been dissloved, broken or shatterd into tiny peices like sand at a beach or at the bottom of the seas, oceans, ect.
Compaction
When erosion occurs sediment travels or gets moved to a lake, pond or ocean were the pieces of sediment compact with each other. The biggest rocks fall the shortest way, the medium rocks fall into the center, and the smallest rocks fall the farthest. Over time they compact and become a type of sedimentary rock.
Fossils
Unlike Metamorphic rocks or Igneous rocks, fossils can actually stay in sedimentary rocks in certain areas because of the amounts of pressure and heat. The sediment protects the fossils and that is what makes them fossils.
Fossil Fuels
Fossil fuels are fuels formed from natural processes the age of the organisms and their resulting fossil fuels is normally millions of years and can extend past 650 million years. Fossil fuels contain high percentages of carbon, coal, petroleum, and natural gas, but I am unsure of the percentages of these materials in fossil fuels. Fossil fuels formed from the fossilized remains of dead plants and animals, if exposed to heat and pressure in the Earths crust over millions of years.