A Roth IRA and a Traditional IRA are both tax-advantaged retirement accounts, but they take opposite approaches to when you pay taxes. Roth contributions are made with after-tax dollars but grow and can be withdrawn completely tax-free in retirement, while Traditional contributions are tax-deductible upfront but taxed as ordinary income when withdrawn.
Savers compare the two because the choice essentially comes down to a bet on your own future tax rate — pay taxes now at your current rate, or defer them until retirement and pay whatever rate applies then.