Assets manager & replacing files

I’m a bit confused with the process in replacing existing PDF documents.
Can someone explain how the management of file assets works?
Files seem to have two different file name types.
There is the filename in the asset manager which is the actual filename before uploading, and then there is the CDN url.
After a file is replaced on a web page, the URL seems to be referencing the original filename which can be very confusing. At first, I thought the file being displayed on the webpage was not actually being updated.
This is an example…
I replaced JulyFile.pdf with AugustFile.pdf but the url (which is also the title of the document when viewed in a browser) still references the original and displays as 611f0bea8ca2074d1a14f2a2_JulyFile.pdf

Also, the asset manager seems to detect duplicate files. I copied AugustFile.PDF locally and renamed it as AugustFile_2.pdf and uploaded it to the asset manager and even though it has a different filename to AugustFile.PDF it still REPLACES the original file in the assets manager.