Concept:
Sedimentary rocks are formed from sediments that are deposited in layers and later compacted and cemented together.
Step 1: Weathering breaks rocks into small particles called sediments.
Step 2: These sediments are transported by water, wind, or ice.
Step 3: The sediments are deposited in layers.
Step 4: With time, pressure causes compaction of sediments.
Step 5: Minerals act as cementing material and bind the particles together.
Step 6: Hence, sedimentary rocks are formed by:
\[
\boxed{\text{Deposition, compaction and cementation}}
\]