Human: What is the difference between a 401k and a Roth IRA? Assistant: 
The main difference between a 401k and a Roth IRA is the taxation of contributions and withdrawals. Contributions to a 401k are made pre-tax, meaning that they lower your taxable income and you only pay taxes when you withdraw the money. With a Roth IRA, contributions are made with after-tax money, but withdrawals during retirement are tax-free. Furthermore, 401k plans have employer contributions and have higher annual contribution limits than Roth IRAs.