Where can one register a domain?

There are numerous websites on the internet that register domain names. Of which, free domains are generally with subdomains, e.g. whateveriwant.realdomain, while it generally costs to buy a top level domain, e.g. advancedtechsolutions. I recommend using websites such as Weebly for registering free domains, and websites such as BlueHost or GoDaddy for registered domains.