.desktop files are a Linux/Unix thing. Basically, it’s a fancy shortcut, usually to an application, which allows specifying additional infos, like e.g. translated names.
In particular, the contents of the application menu are defined by just a folder filled with .desktop files.
Why do I need to put that at the start of bash, desktop, and html files then?
For shell scripts it’s because bash isn’t the only shell; if you leave out the shebang line, Ubuntu will run your script in Dash instead
Nothing unless you want to serve them without some other way to see what file type they are.
You can run bash scripts with bash.
Don’t know what a desktop file is.
HTML has that because webservers used to not have auto media type detection and response headers.
.desktop files are a Linux/Unix thing. Basically, it’s a fancy shortcut, usually to an application, which allows specifying additional infos, like e.g. translated names.
In particular, the contents of the application menu are defined by just a folder filled with .desktop files.
https://en.wikipedia.org/wiki/Shortcut_(computing)#Unix
Because both ways are used. Microsoft relies on file names, linux on the first bytes of the file.