“Icons: What are they good for?” — “Absolutely Nothing!”
Jeremy Wagstaff, in his regular "Loose Wires" column tells some truth about icons in software:
"One day, probably quite soon, people are going to look at the little icon in their software program that denotes "save" and say, "What the heck is that supposed to be?" That's because, in most cases, the icon in question is a floppy disk -- one of those plastic-enclosed disks some of us still use to store and transport data. And, of course, one day there will be computer users who have no idea what a floppy disk is." (from "Iconoclasm, Jeremy Wagstaff, Wall Street Journal, subscription needed")
You should read the whole article, it's interesting. One thing he doesn't mention is that icons don't (directly) depend on the language of the viewer. Indirectly it does, because there are cultural dependencies on knowing for example that a stop sign means stop. But still they are more language independent, in general, than words.
This has two interesting consequences: If I want my software to be accessible to non-English speakers, I can either have it translated (expensive) or include icons as a supplemental way to explain functionality and save the effort and expense of actually translating it. So that's helpful.
As I discovered when I was traveling in Europe though, there are major limits. I found that standard kitchen gear like stoves and dishwashers often had lots of buttons and dials that were only identified by mysterious little symbols. I mean what's the symbol for "rinse only" or "broil"? It was totally incomprehensible.
I assumed that this occurred in Europe to allow the same piece of equipment to be marketed in a variety of countries. I guess in Europe, culturally, people understand the symbols for "broil" and "rinse only." It was greek to me!