What's the difference between Office 365 and Outlook?

Many people think of Outlook as their "email." However, Outlook is just a client with which to access your email. Your email actually lives in the cloud, which enables you to use other clients to access your email, such as on your smartphone, or tablet, or through webmail.

So, Office 365 is your actual email account. Outlook is just a client, or one way of looking at your email.