Even Mesa residents and people in the greater Phoenix area who are good at business may when it comes to taxes just know that they are a bill one has to pay to the government but that one should try to make the bill as small as reasonably possible. They may therefore not really know what a progressive tax is or how various brackets get decided.
As the name implies, an income tax is a tax on the money an individual brings in. The definition of income is broad, and it includes even things one might not think of as income, such as winnings from a contest or a night at the casino. Still, what is or is not income can be a question which presents complex tax issues.