One way to run a program is to execute it using its full pathname. For example, I know that the date program is installed on my system as /bin/date. I can run the program by typing /bin/date directly on the command line:
% /bin/date Tue Nov 8 16:41:51 EST 1994
This is the same thing I would get if I just typed date. When you type date on the command line, you are essentially using a shortcut for typing /bin/date.