<human>:  What is a 401K and how should I use it?
<bot>: A 401K is a retirement savings plan offered by many employers. It allows you to save money from part of your salary before taxes are taken out and set aside for retirement. Contributions to your 401K are deferred from your current income, so the money is not subject to income taxes until you withdraw it in retirement. Additionally, many employers match contributions to your 401K or provide other incentives to help you save. Generally, the money in a 401K should be used only for retirement plans, as withdrawing this money before retirement can incur hefty tax penalties.