Update: Fixed as of iOS 5 — this now says "Info".
Ran into this little bug last night as I was updating some of my iPhone apps:
This heading is shown when you are viewing the description of a specific application's updates. I don't know why it says "iTunes Store" instead of "App Store". You don't have a view like this on iPad — all change descriptions are shown on the Updates tab, which simply has the heading "Updates".
Yes, it's a small, small thing. But now that I've seen it, it bugs me every time I update an app.
Observed on iOS 4.3.