So, the "lecturer" (they're not "professors" here) is talking about the use of signs and symbols as language. This guy is crazy, by the way. The whole class feels like a course in existentialism. We talk in circles about nothing and everything. He has this crazy laugh, too ("HAHAH... hmmm... HAHA... hmm, mmm..."); think Dr. Evil meets the hyenas from The Lion King.
Anyway, it's a Powerpoint lecture and he's showing us pictures of symbols. He shows us an error sign that would have appeared on an old school computer. It's an octagon with a hand on it (like the "stop" hand crossing guards give). He explains how even though it doesn't explicitly say it, most people will be able to gather what the symbol means just because of the context.
How do we know the symbol means "error" or something like it? A few reasons show up on the screen and one of them says something like "When pictures of hands are shown in America, they are often fat and chubby." Whaaaat? No one said anything, like that was a perfectly logical reason or like that even had anything to do with the argument.
I don't know, just a really long explanation of an observation.