Working on an organization consists of building out the systems for getting things done.
Working in an organization means carrying out those processes.
This might seem like an arbitrary distinction at first, but it’s a useful way of identifying the potential impact of your efforts.
An engineer choosing which potato slicing machine to install in the chips factory is working on the business. But the person inspecting the chips for quality as they're bagged is working in the business.
There are enormous downstream effects when you're working on the business. Choose a bad slicer, and you might end up with thousands of bags of poorly cut chips. But you're also in a position to dramatically improve the factory's operations.
On the other hand, if you're the quality control person, you have deep insight into how well the business is operating, since you're on the front lines of it. And if you make a mistake, the downside is capped, since you're not equipped to change things at the process level.
So if you’re evaluating a new job or set of responsibilities, ask yourself: Will I mostly be working on this organization or in it? And on which end of that spectrum will I feel most fulfilled?