A 401(k) is a retirement savings plan that employers offer. Employees can save a portion of their salary into a 401(k) account, up to annual limitations. Employees set a percentage of their income to be automatically taken out of each paycheck and invested in their account.

Employers often match a portion of their employees' contributions. Contributions are automatically withdrawn from employee paychecks and invested in funds of the employee's choosing. Money in a 401(k) plan grows tax-deferred with compounding interest.

If you leave your job, your 401(k) will stay where it is until you decide what you want to do with it. You have several choices including leaving it where it is, rolling it over to another retirement account, or cashing it out.