A computer processor runs programs written in the machine language of that processor. Machine language files are binary files (and are sometimes called binaries), and you cannot read them directly unless you have some very special skills.
There are two kinds of machine language file.
An executable file is a complete machine language program. You can run it as a command simply by typing its name (or a path) as a command. If you want to run an executable file that is in the current directory, write it with ./ in front of it. For example,
./frogruns the executable file called frog in the current directory.
An object file is a partial machine language program. It is designed to be linked to other object files to produce an executable file. You cannot run an object file by writing its name as a command.
Machine language files are also called binaries since they use binary notation.