What does “official budget” mean?

A pre-plan for spending, generally involving an upper limit by category, including not only existing scheduled payments, but also ad-hoc spending.

Like most plans, a budget can be as loose or a tight as you want, and you may or may not follow it, but just building it can result in a more successful approach.

I think most people use a spreadsheet, so they can include some things that are auto-calculated, but that’s not a essential property.