A domain parking page is a page that tells everyone that this domain name has been registered and displays your email address or contact information or any other message that you would like to display. In this way, you can reserve a domain name for yourself and protect it from being registered by another person. If your web site has not yet been developed, the domain services agency with whom you have parked your domain can display an 'Under Construction' default page.
If you do not park your domain, an error message is displayed every time a user types your domain name through a browser. To avoid such a situation, you can resort to domain parking till such time that your site is being developed. When the site is completed, you can update it.
In fact, domain parking is akin to placing the website on hold till your website is ready to be published for the rest of the world. Alternatively you can redirect the traffic coming to this web site to another website that you own. Domain hosting companies offer services for domain parking too. Domain parking allows for publishers to monetize the traffic that comes to the 'still under construction' domain. Advertising links can be placed on the page. It is advantageous to earn through pay per click on the parked domains. If your parked domain name is a popular one, you can consider making use of revenue sharing services from Sedo or Traffic Parking.
Another reason that web site owners resort to domain parking is when they want to sell their domains. If you park your domain with a reliable domain services provider, you stand a better chance of selling it. The 'For Sale' notice can help you find suitable buyers. A domain management service can help you understand the traffic pattern to your web site. This helps in analyzing the potential of the domain and its value.