Google ranks subdomains more or less the same as subdirectories (also referred to as subfolders).
But there’s a key difference, in that subdomains are considered standalone sites and distinct from the main domain.
It’s important to consider the practical impact on your SEO before choosing to place content on a subdomain or a subdirectory.
The Difference Between a Subdomain & Subdirectory
What Is a Subdirectory?
A website is typically made up of different category sections and web pages.
In the old days of HTML coding, a web designer would create folders and put the web pages into those folders.
That’s why they are called “subfolders“ or “subdirectories.”
This is very similar to how file storage works on a desktop computer, where you create folders and put images or spreadsheet files into the folders.
Just like your desktop folders, the online folders would have a name like /green-widgets/. That’s where all the green widget HTML pages would go.