A 401(k) plan is a retirement savings account offered by employers that allows employees to save a portion of their paycheck before taxes are taken out. This means that the money contributed to the plan can grow tax-deferred until it is withdrawn during retirement. Many employers also offer matching contributions, which can help employees save even more for their future. Participants can choose how to invest their contributions, typically in a range of options like mutual funds or stocks. There are limits on how much can be contributed each year, and early withdrawals may incur penalties. Overall, a 401(k) plan is a valuable tool for building retirement savings.