the most information that the average curious person can find out about you with only your IP address (and nothing else) is what region, city and town you are in when you’re on the Internet. They won’t know anything about you (such as your name, etc.) or the computer you’re using.
And actually, what they’ll find out isn’t really about YOU, more than it is about your online connection. That is, it doesn’t know WHO is using a certain IP address—they can only find out, in general, where that computer is.
There ya go…useful (ish)