I'm trying to make a program (Thunderbird) run at startup, but when I go to usr/bin it seems empty. However, if I run $ which Thunderbird in terminal, it tells me /usr/bin/thunderbird.
The usr/bin folder has the option to display hidden files checked. What could be the reason I can't find any files in that folder?
Make sure you are typing in /usr/bin, not usr/bin.
The latter means "look for usr/bin starting in the current directory." For example, if your current directory is your home directory (~), then it will look for ~/usr/bin.
The former means "look for /usr/bin starting from the root directory." This makes sure that the search for usr/bin starts from the root directory /.
To put this another way, if the path doesn't start with a /, then it is assumed that the path you specified is from the current directory.
usr/bin is also called a relative path as it is relative to the directory you're in. On the other hand, /usr/bin is an absolute path.