Programs... just open and run.
Files... however need applications to use most files. The ".EXTension" tells a lot about what possible application could be used.
Since there are some thousand extension I can't tell what you may need.
After all these years, I am almost too embarrased to ask this question.
Many times when I go to open a proram, it pops up a whole list of suggestions to use to open with, when none will open it, it asks for others, that does not help, so by then I abandon the project and move on.