Sedimentary rocks are the rocks that are formed by the accumulation and deposition of sediments. These sediments could be organic or inorganic in nature. Sedimentary rocks are also known as fossil rocks because they contain fossils of plants and animals that lived millions of years ago.

Explanation:
Sedimentary rocks are formed by the following process:

1. Weathering: The process of breaking down of rocks into smaller particles by physical, chemical, and biological means is called weathering.

2. Erosion: The process of transportation of these smaller particles by wind, water, or ice is called erosion.

3. Deposition: The process of settling down of these transported particles is called deposition.

4. Compaction: The process of squeezing the sediments together due to the weight of the overlying sediments is called compaction.

5. Cementation: The process of binding the sediments together by minerals like silica, calcite, or iron oxide is called cementation.

Sedimentary rocks are classified into three types:

1. Clastic sedimentary rocks: These are formed by the accumulation of rock fragments or sediments that have been transported and deposited by wind, water, or ice.

2. Chemical sedimentary rocks: These are formed by the precipitation of minerals from water that has evaporated or through chemical reactions between minerals in solution.

3. Organic sedimentary rocks: These are formed from the accumulation of organic matter, such as plant and animal remains, that have been buried and compressed over millions of years.

Sedimentary rocks are important because they provide clues about the Earth's history and the conditions that existed when they were formed. They also contain valuable resources like coal, oil, and gas.