Bedrock is a natural raw material and block (that you can also place) found in the Fossil layer
just below the surface or in shallow Caves
, together with Stone
You'll need to equip a Stone Mining Cell or better to pull / mine Bedrock.
Obtaining / mining Bedrock is one of the requirements to unlock the crafting recipes each for the Forge and for Bedrock Walls.
Bedrock is then an ingredient to craft the aforementioned Forges, Bedrock Doors, and a number of building blocks like the Bedrock Wall.
Bedrock can also be used to craft Stone Slabs and/or Stone Rods in a Processor (no crafting recipes are needed for that).