I have partial understanding of why a developer will have a filename like afs342sf.css opposed to something more readable like main.css - I do not believe that the developer named the file manually; I'm sure it was done programmatically upon insert into whatever database. I'm a bit baffled on why this would be needed, and how it will be called.
If a database has a table with, and excluding others for simplicity:
file_id, file_name, file_display_name, file_size.......... etc.
When called for data it's using file_display_name (afs342sf.css or simply afs342sf) as a reference - href="/yourhost/www/afs342sf.css" - what on earth is the difference when someone can easily use the same GET request info, or have I got this theory all wrong? - I'm a paranoid one typically (apparently good for security) and have confused myself because it could also be the id for it, but isn't that giving away too much? Then there's the thought of what if the program changes the filename upon every request; could it get lost when other requests are incoming, and it doesn't have a fixed address name?
Last but not least, I would much appreciate it if anyone could post any links to pages that could help with stealthy, or concealed file retrieval methods. For the record I do not hide the .php extension - being self taught and learning from a trusted community is overwhelming for knowledge.
You're right, it's not named manually. Arbitrary filenames like that usually mean they are generated with a tool like Assetic. This is primarily used for files that have to be converted before being put on the web (SASS to CSS; Coffeescript to Javascript).
Assetic also has a cache-busting plug-in that generates filenames based on the hash so when the contents change, browsers will be forced to fetch the new file (this is a standard cache-busting technique). This is useful because static files usually have long expiry dates, and there's no other way to alert the browser that the file has changed.