The term "401" often refers to a type of retirement savings plan in the United States known as a 401(k). This plan allows employees to save a portion of their paycheck before taxes are taken out, which can help reduce their taxable income. Employers may also match contributions, providing an additional incentive for employees to save for retirement. In a different context, "401" can also refer to a HTTP status code indicating that a request requires user authentication. This means that the server is expecting the client to provide valid credentials before granting access to the requested resource.