e is the event, which includes the target, the thing that triggered the event. So e.target is the element, which you can get the value of with .value as usual
Ok, then e is just so the .target.value can read info from what caused the event(in this case a change to the dropdown)? Without the e the code doesn’t know where to look for that info, as in if you ran that code segment without the e’s nothing would log to the console?
the callback function always is passed an argument even if you don’t write a parameter, if you want to capture the argument you can use a parameter
also the arguments object is useful but a bit clunky to use, a parameter is much easier, so we tend to prefer writing a function with parameters instead