All domain registries, whether you register a top level domain (.com, .net, .org) or a ccTLD (.ph, .co.uk, .co.au) make registrant information available to anyone who wishes to view them via the WHOIS function. This means the information you put there can be seen by anyone, anywhere, anytime with a simple click using a domain lookup. It's like telling strangers where you live and how to contact you.
Spammers also use robots to crawl WHOIS and domain lookup sites to mine information. You're at risk of receiving domain-related spam and other forms of privacy intrusions.
WHOIS is a database query system that provides registrant information and other details about a domain nameholder.