The domain of a website is a unique name that identifies it, which in this case is your online store.
Once you have decided on the domain name, you will have to contract it with the provider of your choice, bearing in mind that you may need to have a mail service associated. Some providers offer a basic mail service for free, and with others you must contract it separately.
If you take out a domain contract with Nominalia, you will have a domain with everything you need:
Click here to take out a contract, search for the domain you want and follow the steps to set up the contract.