[AccessD] OT: What does Last Date Accessed mean?

I want to list the files in a folder on a form so a user can select the file
they want to open.  I can list these three dates to help give more info, but
they don't seem to make sense. 

I think I see that Modified can be earlier than Created if the file was a
copy and hadn't been modified since the copy action.  

But what does Date Accessed mean?  I opened a file, looked at it, then
closed it w/o changes.  The Date Accessed did not change.

I did a Google search, but nothing helpful showed up.

Thanks!
Dan