You can browse through the folders and compose emails and almost all functionalities. Use Find Someone to check your GAL information, Contacts is the same as Outlook Contacts and so on. It is quite straight forward; hence browse through each option to know more.
To enable/disable this feature to the end users, you may control the Feature Outlook Web App. If you enable OWA feature in user mailbox the OMA feature also gets activated automatically.
What I did not see is the log off button, so you may close directly. As Microsoft warns, you should change the password immediately if you loss the mobile device.