With 'Different' you can choose how you will receive your notifications - SMS, Email, or both.
When you click on the link of the first request you receive, a "Vendor Tutorial" will appear on your screen. When you have finished reading the tutorial, you will be directed to your notifications page (under the 'Settings' tab).
In your notifications page (under the 'Settings' tab), you need to select for each one of these options if you will receive a notification by SMS, Email, or both.
You can edit your notifications any time from your 'Settings' tab.