After one year you need to renew your domain name so that your website doesn't get lost. Generally when your domain is about to expire your domain registrar will send you a reminder mail regarding the domain renewal. When your domain name expires you can renew it within one month. If you don't renew it in this period it goes into a redemption phase. It stays in this redemption phase for 15 to 30 days before it is then available for purchase again at a normal price.
