You can park your domain name after you purchase it until you decide what to do with it. Once you register a name you typically point it to the website you want to appear when someone types in that domain. Until you do that the domain needs to resolve to something. With most registrars it will point to a standard page which typically promotes their services.
Generate Revenue When the Domain is Parked
Some companies offer a service to let you potentially make money when the domain is parked. Instead of showing a page that promotes their services it will show advertisements. You receive a portion of this revenue. How much you actually make depends on how many people happen to visit the page. If it is brand new that will probably be next to none. However if you purchase a domain that has been used in the past then there many be some traffic to the site.
CashParking with GoDaddy
A few advertisements are placed or posted on these idle domains. A webpage appears to the visitor when they visit the domain and each click on the ads placed on it brings you revenue. This is the pay-per-click advertising model. The revenue sharing model is pre-fixed. There is a plan whereby you make 60% and a plan where you make 80% of the revenue generated. Both plans have a monthly fee, however you can monetize as many domains as you like. Once you get the plan you add them to your CashParking portfolio and the rest is taken care of for you.
Parking and Domain Services
You can also obtain a godaddy discount on domain registration, domain auctions and all their products.