You can see it if you go to the page history. It's intended to give you tricks about what was changed on that revision. Plus, if you are creating a new section, it gets that field's title.

"chris2fr" contact@infopol.fr escribió en el mensaje news:442A4E23.2030105@infopol.fr...

If I fill out the wpSummary field, nothing seems to be done with it. What is this feild for ?