Let's say someone wanted to find out about something and that that person had a internet connection.
Ahh well, I'm not into a story like that.
What I do when I want to find out about things is to do a
Google search first, try something like "file extentions"
And if I have a verry specific question about a subject, and can't find it on a web page, I use google to find a related forum.
In general, all you want to know about anything is out there somewhere on the internet.
Good luck !