Alert and notification option in job properties
Magier -- The alerts are designed to allow you to capture and sent a notification for just about any condition that occurs on your SQL server. One common practice is to have the SQL agent looking for different fatal error severity levels that could be returned as a result of an error being raised from an executed command. Or for specific errors that are reported in the SQL logs that could indicate IO issues right up to database corruption. 

Brent Ozar has a write up about some of the common alerts that he recommends as part of their sp_blitz procedure. 

You could most certainly add many more if you don't have an additional monitoring service running to give you a heads up when something isn't within the range that you're expecting or warnings/errors are reported in the SQL logs.