Outlook is an email programme, part of MS Office.
You can configure it for use as your email if you want, and if so, will receive email to both your ISP email, and Outlook. I have configured mine for my main email programme. I'm actually on AOL, so whenever I receive an email to my AOL email, it comes through to Outlook, which I prefer to AOL.
Go to Tools, Email accounts, New, and configure from there. Try googling Outlook 2007 configure, and it may provide the solution.