I’m purely a visual person. I cannot put clothes into a dresser drawer. If it is out of sight; it’s out of mind. It’s that bad. Thus being able to view all the files in a repo for a given commit really helped drive home how Git is so different from other source control systems.
Going back to my random-example repo, suppose you want to see the state of the repo as of the first commit on master.
Navigate to the Code tab and make sure master is selected. (If you want to view the state of a repo for a commit on a different branch, use this Branch:master dropwdown button to change to desired branch.)

Now scroll all the way down to the original commit. You’ll see highlighted in the next image a <> button that displays a tooltip Browse the repository at this point in the history.

Clicking on this <> button takes you back to what looks exactly like the repo homepage, but with one key difference…

Instead of branch:master or branch:readme-draft, you’re now seeing this Tree:ad98b093 thingy.
What’s a tree? This question gets into the internals of Git, which we will learn together this year! To be honest, all I know right now is that every Git commit has a tree, so this dropdown button label is saying, “show me the files for this commit id.” You’ll also notice that

You’ll see that this Tree:ad98b093 commit id matches the id in the far right.
You might be wondering why the dropdown doesn’t show the list of all the possible trees to view. My guess is this list would be come unmanageable pretty quickly. And people probably don’t need to look up the state of a repo at a given snapshot very often.