Think of the domain as a empty lot of land.Developing a domain is much like land developement.Generally speaking it involves putting up a site located at that web address.The site could be a simple parking page with just some ads on it or it can range from a simple one page information page, all the way to a major site with scripts
and even a member base like namepros.Often developement can involve monetizing the site which allows the domain owner the ability to generate some income from his web property through advertizing or charging fees for use of its contents.