People on my team and those I mentor often ask me what the difference is between junior versus senior product managers.
I think it revolves around two things: handling ambiguity, and dealing with scope.
A junior PM works on an individual feature. A senior PM works on a feature area, which involves multiple features. A principal / lead PM works on an entire product comprised of multiple feature areas, or even a suite of products.
A junior PM can be given a clear problem and clear solution and execute it well. It doesn’t mean the work is easy, but it’s clear.
A senior PM can be given a clear problem with an _unclear_ solution. Here, the ambiguity is in figuring out the right solution and why it’s the right solution before executing it well.
A principal / lead PM can be given an unclear problem _and_ an unclear solution. They first need to figure out which problem is the right one to solve before figuring out which is the right solution and why, before executing it well.
When you combine the two, you get a sense of the differences between levels. On the one end we have junior PMs who work on clear problems/solutions on one or more individual features. On the other we have principal / lead PMs who can define product strategies and steer an entire product towards the right outcomes for both customers and the business.
There are surely other ways to define the roles, but I’ve found scope and ambiguity to be the two most consistent ways across companies and industries.