Request for more information about plug in options

Hello,
I am looking for more information about each expiration type option and their functions, in particular;
Private- does this just mean only users from back-end can see a post expired to private?
Stick
Unstick
Category: Replace, Add, Remove- more details on how you might implement this for best use.

Also, is there a way to send notifications to an email for posts of a certain type or tagged with a certain category?
for example: If I have different departments and they all post content, once a post expires, I would like it to be sent to only the specific department contact not all emails on the list.

Thank you!