Here . just means "the directory". Let's put it another way. If a file/program is executable and in your path and you have permission to execute it you can execute it from anywhere.

On the other hand, if it's not in your path you need to execute it as follows:

./my_program (and it's easier to do it from within the directory).

The ./ basically tells the shell "hey, don't wander off searching the path, just run the program that's in this directory".

Generally, executables will be found in directories like /bin and /sbin.