In NextJS anything you keep inside the pages
folder is considered a page or subpage, lets's say you have created the components
folder inside one of the pages
folders like below. Then you can access the components inside this folder as pages, so you can access this component with the below URL.
https://baseUrl/admin/components/componentName

So in NextJs, everything we put inside the pages folder is considered an individual page. If you want a separate space/folder
for components you can create feature-level components outside the page folder like below.

Now components added in this feature folder are not accessible as a page and you can reuse these components as you want.
I hope this answered your question. Happy coding!