Using the internet for surfing different sites does not mean you actually know the meaning of a domain. If someone asks what is a domain, Many people would simply answers its a name. Yeah of course its a name representing something but there is much more to know about it.
What is a Domain
Domain can be considered as a place where we can use the place to show up something. For example beinglegends.com is a domain where we show up our articles online.
Can two persons have the same domain
Once if a domain is used by a person it cannot be own by the other until his registration completes.
One can own mutliple domains but mutliple persons cannot own single domain.
How to buy a domain
There are many online sites like Godaddy , Blue Host and much more. These where the places you can by Domains.
If you want to develop a product or a site or something to a good level and want to show it on the internet then you should choose a domain which suits your product name or something related to it. You can do it by buying the domain and making your product visible on the internet.