When you buy a government bond, you lend the government an agreed amount of money for an agreed period of time. In return, the government will pay you back a set level of interest at regular periods, known as the coupon. This makes bonds a fixed-income asset.
Once the bond expires, you’ll get back to your original investment. The day on which you get your original investment back is called the maturity date. Different bonds will come with different maturity dates – you could buy a bond that matures in less than a year, or one that matures in 30 years or more.