Profile Updated vs Last Active

Can anyone help me understand the difference between Profile Updated and Last Active?

I realize that many times, the day/time stamp will be the same - if a subscriber opens an email, the Last Active and Profile Updated will both reflect the time the email was opened.
I’m wondering - is there any case where they could be different? For example, at our brick & mortar retail stores, employees can update a customer’s information using the list’s subscription landing page - and I thought perhaps this would be recorded as Profile Updated, but NOT Last Active.  However, in my own tests, this does not seem to be the case; both fields continue to be the same. This leads me to more questions:
1 - If Profile Updated and Last Active are always the same, why are both included in a subscriber’s profile?
2 - If they are not always the same, why can I export Last Active, but not Profile Updated?

Any information is appreciated! Thank you!