People should be first, because they are the most important asset that your business has, essentially they are the living body of your organization and nothing gets done without them.
You must ensure they know the “WHAT” of their job, by clearly defining their responsibilities. This is the primary directive, without this there will be confusion and people will do what they think they should, and not necessarily what your company needs done.
Process is next. Once your People know their responsibilities, they need to know “HOW” they should go about executing those responsibilities.
Process is the sequence of actions that they need to perform in order to get a desired outcome. In the absence of Process activities will be ad-hoc, things will take longer and in some cases work will be problematic and error prone.
Once your people know what they need to do and how to get it done, then the Product will be the natural outcome of their labors. Their focus becomes the Product.
The 3 Ps means the right people applying their responsibilities, using the process, and having a product focus, is what’s needed to make your company great.