What is this download?

Question

Windows

Sometimes, when you open a folder containing many files (such as images, documents, etc.), a green bar appears at the top of the window.
Screenshot: https://prnt.sc/g7elyj
In this screenshot, do not pay attention to the fact that the search is in progress. This screenshot is needed to make it clear which green bar is in question.
What it is?
Is it something to do with the Windows File Indexing Service?
OS: Windows 7.

Answer 1

just loading a list of files in a folder. the strip itself is actually fake and follows a certain average timer, since the number of files is not known in advance.
you can see it by inserting a obviously non-working DVD. from which nothing will ever be loaded.
indexing is different. it's for searching. and this is handled by a separate background service. it is hardly connected with your opening of a folder.

Answer 2

What it is?
Is it something to do with the Windows File Indexing Service?

This is the search time indicator.
It is necessary so that in the event of a long search, the user does not worry that the computer is frozen, and sees how much more to wait.
Of course, all this is directly related to the file indexing service - if the files are indexed, the bar runs quickly, if the files are not indexed, the search takes a very long time and the bar barely moves.