You can own a domain even if you don't have it associated with a webpage at this time. This will park the domain at the registrar' domain, but as long as you pay the domain fee, you are the legal owner of the domain.
Therefore, you can own multiple top-level domains to ensure that other people's websites don't have the same domain name as yours.
Canheende you have a vision that takes time to mature before you can start up your business, but you know which names you want to use. Then you can buy the domain and leave it parked, so you have it ready the day you are ready to create a website and realize your vision.