Withholdings are “pay as you go”. Based on how you fill out your W4 regarding dependents and other income, your employer withholds a certain amount of taxes from each paycheck and sends it to the government. Withholdings are just an estimate.

After the year is over when you go to file your taxes, you settle up. Too much withheld, you get a refund. Too little withheld, you owe more.

Yes, the government uses your tax money for infrastructure, social programs, services, schools, and anything else the government provides. They don’t invest it as much as spend it.