What defines a "Progressive" tax rate structure?

A progressive tax rate structure is defined by its characteristic of increasing marginal tax rates as a taxpayer's income, or tax base, increases. This means that as individuals earn more, they pay a higher percentage of their income in taxes. The rationale behind this system is to impose a greater tax burden on those who have a higher ability to pay, which is intended to promote equity in the taxation system. Essentially, lower-income earners pay a smaller percentage of their income in taxes, while higher-income earners contribute a larger portion, which can help reduce income inequality and provide necessary funds for public services that benefit society as a whole. This structure contrasts with other tax systems that may apply constant rates or decreasing rates without regard to income levels, ultimately leading to different impacts on taxpayers across various income brackets.