Essentially, when you register a domain name, ICANN requires a physical location and name of the owner, so that if you’re doing something illegal or infringing on trademarks or anything like that. (more info here)
That’s all great, you have nothing to hide, right? Well yes and no. The problem is that the database is public. If you’re running “AwesomeCustomCoasters.com” and you have a customer who gets really angry because their coaster didn’t absorb as much condensation as they thought it should, they can look up your records and drive to your house, call your home phone number, or spam your email address.
To avoid this, ALWAYS SIGN UP FOR DOMAIN PRIVACY. Most registrars charge an extra $10-15/year for this, but that’s why I use NameCheap.com, it’s only $3/year and the first year is usually free. This will replace your information with something generic, like “whoisguard” with a different address and phone number. This will NOT protect you from law enforcement, the domain privacy company will give your information out to the agencies who have proper authority, so don’t get any funny ideas!
If you’re not sure if you have privacy already or not, check it out here: https://whois.icann.org/en
If your results show information that you don’t want the public to see, go buy some Domain Privacy!