This is where a company tries to steal your domain name.
You receive an official looking letter or email requesting you to renew / transfer the domain to them.
I get these quite often and they do look legitimate.
Never reply, give credit card details or transfer your domain to them.
I’ve also had customers getting phone calls from companies who are about to sell a similar domain to yours, on looking this domain up they find you, and being nice think you should buy the domain instead of their customer. Don’t be fooled.