When you register a new domain name, you have to give your name, address, email address and other contact details as the new owner of the domain.
This confirms that you, and not another individual or another entity, legally own the name.
If you register a new domain in the standard way, then your personal details will be available to anyone who knows how to look them up.
One way to check this is simply to use whois.
net - typing the domain name into their search box gives the name, address, email address, and phone number of the owner and the expiry date of the domain.
Why would this be a problem, and why would you wish to make your domain name registration private? Since the email address is publicly available to anyone, it can be added to spam lists.
In addition, since your physical address is available too, you will inevitable get snail mail contact, offering things like 'discount' registration if you switch to a new registrar.
Or, you will get unwanted calls from telemarketers, who will know a bit about your business or your interests by simply looking at your web site.
As marketing campaigns become more sophisticated, you will be subject to all kinds of unwanted contact.
If your web site content is political, contentious, or may annoy certain people, you may get unwanted emails or calls which are abusive or annoying.
Apart from these concerns, perhaps you just don't like the idea of anyone knowing which domains you own.
So how can your protect yourself? One method is to pay a little bit more and get a private domain name, also called a private registration, or an unlisted registration (similar to the idea of an unlisted phone number).
This means that the registrar still has your details, but they are not accessible to the public.
Someone searching in whois.
net will only be able to see the registrar, the date of registration, the expiry date, and the name of the servers carrying the site - but none of your private details.
For any web site you mean to develop commercially, or for any site which is controversial in any way, private registration is a good idea.
Most good domain name registrars offer this private domain name service as an add-on at the time of first registration, and it can also be applied to existing, transferred or even back-ordered domains.
Switching to a private domain registration does not change anything else - you still have full control of the domain and can sell it, renew it, or change the nameservers.