"A domain transfer" is to transfer domain name from the management under one registrar to another registrar. Besides your domain name will be automatically renewed 1 year after transfer process is complete, in under condition that your domain name must registered or renewed at least 60 days.
Domain name transfer should be proceeded at least 30 days before domain name expiration date, because there will be domain name transfer approval in the process. You have to approve domain name transfer out from the current registrar and then from the another registrar you want to move your domain to. It may take 5-7 days or more for this process.
Remark : As a registrar is only responsible for the management of your domain records, this transfer should in no way affect your website, relevant email or DNS.
1. Transfer domain name to the same registrar or Reseller Transfer or Ownership Transfer This process spend the time less than domain name transfer to different registrar. But you have to inform your provider to proceed it for you. You may asked for further information about your domain name.
2. Transfer domain name to different registrar (Registrar Transfer) This process spend more time than domain name transfer to the same registrar. To prevent that you may not transfer domain name in time, you should make a process at least 30 days before domain name expiration date.