Subdomains to help organize and navigate to different sections of your main website. Within your main domain, you can have as many subdomain as necessary to get to all of the different pages of your website.
You can actually use any text you’d like as your subdomain, but make it something that’s easy for users to type and remember. Learn more about domain owner.
Subdomains make internet life easier:
The Domain Name System(DNS) is place to create Internet to regulate the domains and subdomains. Because DNS, we only need to remember the names of subdomain.
How to use subdomain:
Subdomain is main website that considered a separated search engine. Besides that companies use subdomain for a reason, that separate identity in search engine while a part in main website.
Subdomains vs. subdirectories:
Subdirectories are another similar form of subfolders that can be used as extensions of your main root domain and subdomain typically comes before the main domain in your URL, a subdirectory would come after.
Lets look whether subdomains or subdirectories are better :
Hosting fees:
Subdomain separated websites and also hosted on separated hosting plan. You need to pay separated for each subdomain. While subdirectories you need pay only one hosting fee. And the amount depend on overall size of website as how much speed required.
Customization:
Subdomain, you can customize your website content to cater to different regions, users, and products, If you need unique content for each of your different subdomains.
While, you don’t really need to create such highly-customized content, you may be better off using a subdirectory because this may easier and not include extra hosting fees.