A domain transfer is a process in which a domain is moved from one domain registrar to another registrar. There are many reasons why owners of a domain may choose to transfer their domain to another registrar, for example: price, quality of customer service, and ease of use, etc.
The domain name keeps working as it is and whole transfer process is transparent. In most cases, each domain transfer will be automatically renewed for 1 year from the current expiration date.
Please visit Domain Tranefer Checklist here for more details.