in .gitignore what is the difference between using
/bin
and
bin/
And how would I make it so that it removes a certain file, no matter where it is?
*/*.ext
A leading / anchors the ignore pattern at the point in the tree where the particular .gitignore resides.
A trailing / means that a pattern will only match a directory (and so all the files in that matching directory).
You can have both, e.g. /bin/ will match only a directory called bin and only at the level of the .gitignore file.
A simple *.ext will match any file ending with .ext anywhere at or below the level of the .gitignore file in which it appears.