Domain transfer means changing to another company to manage the registration of your domain.
This means that if you registered your domain within a company, and for some reason (price, service, quality, support) want to change the administration of that domain to another company, you may do so using the domain transfer process.
It is important to mention that in the domain transfer process, the current registrant may reject the request for transfer by some reasons such as:
The domain has expired.
Check-in is less than 60 days.
Registrant data have changed in less than 60 days.
The confirmation email sent to the domain transfer current contact was not confirmed.
Among other reasons.