why is the javascript not javascripting

my html isn't javascripting even though i put my <script src=app.js></script> directly above the </body>

you'd need to do

<script src="app.js"></script>

(you need the quotation marks for it to work)

no but like the i do it correctly with the quotes and none of the code runs
like the tab just freezes

maybe you have a piece of code that is never exiting? did you misname a for loop variable or something/mess something up with while loops? (It's a common mistake to misname an increment variable when you start getting into that kind of thing.)
In general, it means some part of the code is always running without stopping.