The ./ is required for running scripts/programs unless you add that directory to what is called the PATH or Environment Variable. ./ tells bash to look for the program/script you want to run in your current working directory.
The PATH variable names what are essentially global folders, folders that you can run programs from without having to be in them to do so.
You can add Firefox to the PATH Variable for the current session by running the command :
export PATH=$PATH:[PATHTOFIREFOX]
If you want to add it to the PATH variable permenatly there is a guide on how to do that
here. This guide refers to commands that you would use in a Perl Script but farther down it has instructions on how to modify your Bash Startup Script so that a directory is added to the PATH Variable.