A domain must be unique (for example there can only be one single Yahoo.com) and must be registered with a domain registrar (ie. NameCheap); while for sub domains, users can freely add it on top of the existing domain as long as their web host provide the service. Some would say sub-domains are the ‘third level’ domains in the sense that they are simply “sub folders” under the domain root directory, normally used to organize your website content in different languages or different categories.
^ March 16, 1992 memo from Mariam Leder, NSF Assistant General Counsel to Steven Wolff, Division Director, NSF DNCRI (included at page 128 of Management of NSFNET, a transcript of the March 12, 1992 hearing before the Subcommittee on Science of the Committee on Science, Space, and Technology, U.S. House of Representatives, One Hundred Second Congress, Second Session, Hon. Rick Boucher, subcommittee chairman, presiding)
People often think that a web host is the main cause of a slow website but, this is often not the case. When picking a provider, it's important for find a hosting provider that is close to your users and has a good amount of RAM and fast CPU power. Beyond that, it's often the way the website is set up that slows it down for users. To ensure that your website speed is optimal for users you need to make sure you pay attention to the following:
When you purchase or transfer a domain to Google Domains, you can immediately start creating your website with one of our website building providers. Plans vary in cost, and options include secure and reliable hosting, customizable templates, and powerful features like drag & drop creation and mobile site-management. To learn more, visit the Help Center.
Yahoo Small Business services are intended and designed to meet the needs of personal and small business websites. This is why some of our plans offer unlimited disk-space, data transfer or email storage. It is not appropriate to use our services to support large enterprises or for levels of demand that impose undue burdens on our systems or negatively impact use by small, independently owned and operated businesses. If the bandwidth, data transfer or email storage of your website or email present a burden on the experience of other users or on our internal systems, we may, in our sole discretion, act to restrict the resources being consumed by your website, including by limiting how fast your disk space and email storage space can grow.
Many services offer a low "starting price," but require you to prepay for two or three years of service to get that price. After the promotional period, the renewal price for some services can be two, three, or even four times the initial promotional pricing. While the initial deal might be incredible, the cost of transferring your site (or paying the added fee) in a couple of years may be something to consider.