A valuable clip from How to Write Articles and Essays Quickly and Expertly by Stephen Downes:

• Argument: convinces someone of something
• Explanation: tells why something happened instead of something else
• Definition: states what a word or concept means
• Description: identifies properties or qualities of things.

I know these words are often found in other contexts, especially in the computer world (arguments = parameters). But what is important to remember is that these are all neutral words. By this I mean that they each can be used for Evil as well as for Good: an argument might convince someone of something false or dangerous; an explanation might be based on a falsehood; a definition might be chosen to advance a mendacious agenda; and a description might be designed to create a false image of a person, place, or situation.

We see a lot of this sort of stuff in politics these days.