So what exactly is a "premium" domain? Premium domains are easy to type. They are memorable, they likely describe your product or service offering succinctly, or the name is simply unique, unusual, and brandable.
Your name can be used several different ways. Furthermore, if you are purchasing a purchasing a .com domain, you are buying the gold standard of domain names.
As with other assets, an investment in a premium domain name will likely increase over time.