Do you know that when you register a domain name, the registration details are available to anyone, who searches a public database online?
The details, which are stored in what is called the WHOIS database, could include your name, address, email and phone number.
Some spammers mine this for email addresses or, even, for stealing or transferring your domain name.
Domain privacy prevents anyone accessing your data when they search for the owner of your domain name. Depending on the purpose of your website, you may or may not want this data visible.
Most registrars charge a yearly fee for WHOIS domain privacy.