[Update: I've created an extended version of this thought. Read it here.]
In short, it's how you run your business.
Company Operating System (Company OS) covers everything from your company's strategy and people to processes and finance.
You may have designed it, or it has emerged and is manifested by how you operate.
My Company OS framework looks like a flywheel:
It contains five main elements:
All of these elements contain sub-elements that need to be in place for any company to function well.
For example, the people element necessitates that you:
Remember, you have either designed how these work, or they have emerged and are manifested by how you operate.
I've seen some happy cases where Company OS is in an excellent state by emergence.
But more often than not, there are ways to improve your Company OS by design.