People use what I post on my webpage?

So I have a googlepages webpage. I put a couple of the papers I wrote for my physics classes on it and figured that was that. I figured I would be the only one who ever looked at my webpage, and perhaps some people I told about it. Well, I was wrong. Today I get an email from some teacher at Sapientia University in Tg-Mures, Romania. He is like I am using your paper on the heat equation and wanted to know about something that was not clear. So I am like hmmmm. People do use the my webpage after. I thought it was cool to get and email from a random guy from Romania anyway.