Once you register a domain name you can

1) develop it into your desired line of business website or

2) have it forward to another of your domains/websites

3) create a website using affiliate links (selling goods or services from household name or online only merchants) for a commission on a pay-per-click, pay-per-action(sale), pay-per-call, pay-per-text basis or pay-per-lead(sign up) basis.

4) if you are too busy or have no technical knowledge of how to create your own website, you can simply leave your domain parked, (this term has changed from its original term back in the mid 90's where you simply had a holding page, nowadays you can show that your domain is for sale AND make a regular income from it much like owning a property and renting it out!

a) with a holding page from your ISP that your domain has just been registered or saying "under construction" - until your website is ready or

b) why not create an income (monetize your domains) allowing paid for pay-per-click advertising on your domain whilst you decide and simultaneously advertise your domain for sale - this is known as domain monetization.