In Outlook 2010 on my Win8.1 desktop, the Data Files tab of Account Settings shows I am using two pst files. The default is outlook.pst. It contains all my personal folders, contacts, and everything except my inbox and sent items folders. The other is myemailaddress@cox.net.pst. It contains only my inbox and sent items folders. Why would Outlook use two pst files? Can I combine them into one pst file?

Also, the Address Books tab shows two address books: Mobile Address Book and Outlook Address Book. Why is that?

I am about to replace Office 2010 with Office 2013 and would like to understand these two issues before I begin that project.