I feel like adding the bedrock abstract definition from LoperOS, it’s from one of my favourite blog posts:
A bedrock abstraction level is found in every man-made system. No recoverable failure, no matter how catastrophic, will ever demand intelligent intervention below it. Repair at those depths consists purely of physical replacement. [1] No car crash, however brutal, will ever produce piles of loose protons and neutrons. When a Unix binary crashes, it might leave behind a core dump but never a “logic gate dump” and certainly not a “transistor dump.” Logic gates and transistors lie well below the bedrock abstraction level of any ordinary computer.
From Loper-OS