I don't have a well defined idea on how the tax system works in the US, the few things I know is that they are paid to the IRS every amount of time (yearly probably) that there's an interest/additional fine after retarding a payment and there's a difference between active and passive income (e.g salary or bank interests, but I know whether there's a distinction in terms of percentage imposing). How does it work for a normal working layman that is, for example, an employee? How often should he pay the IRS? Does he have to pay each month a portion of his salary in taxes or does he have to gather the money on a yearly basis in order to have the fixed percentage of his annual reported salary (which is the sum of the 12 monthly salaries)?
For convenience, you can have your employer withhold taxes from each pay check. You can also send money to the IRS quarterly.
The IRS prefers a steady predictable revenue stream and will fine you if you underestimated your income and make a balloon payment for the fourth quarter, even if the total amount you send them over the course of the year doesn't change.
State taxes work the same way. State taxes are deductible from Federal taxes, to an extent.