LOOK AT WHAT ALL THESE COLLECTIONS OF SITES AT SHAREPOINT ARE
This is the default site collection in which you can create your Intranet. It is the perfect place to create new team sites, service sites, document management sites. You don't need to use this particular site collection for Intranet, and you can always create a new one (more on that later in the post), but this one has it Cleanest (shortest) URL that's easy to remember!
The second site collection in the list is / portals / hub. This is a site collection that contains all the videos that you would post to the Office 365 video portal. I wrote a detailed article on Video Portal – check it out. Office 365 Video Portal is like an internal YouTube for your organization. You can publish all kinds of videos and organize them by channels, like on YouTube. It can be very useful for training, marketing and other corporate videos.
You can see or not this collection of sites in the list. If you do, this site collection is a dedicated space with the community features enabled. It allows administrators to manage discussions in a virtual environment. Honestly, I don't see this feature used by many organizations, so I wouldn't sweat it if I were you. Just know what this site collection is in case you see it, and let's move on! If you have free time, you can read more about this site collection here (official Microsoft article).
This is the site collection responsible for searching your SharePoint environment. Whenever you search in your SharePoint (i.e. using the search box in the upper right corner of the SharePoint site), this site collection (officially known as the Search Center ) processes the requests and displays the results for users. If you've always wanted to adjust how your search results are displayed or how the search query / logic works, you would modify the Search Center (this particular site collection). You can also create additional research centers (site collections) to provide users with an alternative search experience, but that is the subject of some future blog posts.
For more information, see this link,
What are all these site collections in SharePoint?