What are progressive, regressive, and flat taxes?

Question

what are they used for and who do they favor?

Answer 1

progressive - the higher your income, the higher your tax rate

regressive - the lower your income the more you pay

flat tax - everyone pays the same rate

The current US income tax system is progressive.   Some states are also, and some have a flat tax.

Progressive favors lower income people, with the theory that people with more money can afford to pay more tax.  Regressive favors people with high incomes.