what is sedimentary rock?

A sedimentary rock is a rock that is formed through the deposition of sediments over time. Sediments are just the broken down, weathered, and eroded remains of other rocks.

This is in contrast to the other two types of rocks igneous and metamorphic.

Igneous rocks are formed from molten magma drying and solidifying. Metamorphic rocks are formed under intense heat and pressure, but without being completely melted down into magma.

Rocks can become sedimentary rocks through the accumulation of sediments and then undergo differing degrees of metamorphism through varying degrees of heat and pressure -- becoming more solid the greater the metamorphism.

Sedimentary rocks tend to be less solid and more crumbly like a sandstone than their igneous or metamorphic counterparts.