If you were to see WordPress as a house, the Administrator is the owner of the house.
Similar to how the owner gets the keys to the main door in the house, the Administrator in WordPress gets the main access to the WordPress dashboard.
Upon entering the house, the owner will get to see the rooms. In
It’s the same in the WordPress dashboard. But, instead of rooms, you get to see navigations. Each and every navigation has it’s own purpose just like how every room in a house has it’s own purpose.
For example, there is the Posts navigation which allows the Administrator to publish a new post or view all posts that are published or saved as draft. There is the Media navigation which allows the Administrator to upload new media files or view all existing media files that have been uploaded.
Just like how the owner of a house has the right to do literally anything he or she pleases, the Administrator of WordPress is also able to do so. If the owner of the house wants to burn the house down, there is really no one stopping him or her. Same goes to WordPress. If the Administrator wants to ruin the WordPress installation, he or she can gladly light up a malicious code into it.
But of course the above is not something anyone in their right mind would do. Unless, he or she has various types of personalities like the guy from Split (2016).
My point here is that the Administrator in WordPress can do anything in a WordPress dashboard.
From the top of my mind, here is the list of things an Administrator can do in WordPress which other user roles are not able to do: