What does re-installing (from admin) WP fix?

Re-installing WordPress from admin, downloads a fresh copy of WordPress core and installs it. Circumstances where that might be useful, is when you think WordPress might have been tampered with or when errors keep popping up saying files are missing that relates to the core. You can also manually download and reupload the files if you prefer, many people do because while both methods retrieve from the same location, if you download it you know you did it and can check it before reuploading.

I greatly appreciate the thorough response that I can comprehend.

Questions:

1). How can you check it?

if you download it you know you did it and can check it before reuploading.

2). I am not being a jerk here, I want to understand the jargon:
Doesn’t “reupload” mean that you are repeating an upload?

Confessions: I can FTP. But…
I have no idea how to install WP, period. I have used installers on my hosts and home systems. (I have two WP installs – I can’t even figure out how to pull up the local sites in a browser on my home machines.)

Conclusion: So I had better just re-install through admin for now. Sigh. Lame!

Thank you. Cheers!
– Toni