401k matching contributions are extra funds your employer adds to your 401k retirement account based on how much you contribute from your own paycheck. For example, if you put money into your 401k, your employer may match a portion of it, helping you grow your retirement savings faster. The exact amount and rules depend on your employer’s plan, but matching is essentially free money that rewards you for saving. To keep the matched money, you may need to stay with the company for a certain amount of time, which is known as vesting.