If you want to receive email alerts, you or someone has opted you in for you. The email alert shows:
The metric being monitored (with a timeframe)
The percentage of the change compared to before
The account, campaign, and monitor name that triggered the alert
The current results
The absolute change that happened
The results from the previous timeframe chosen for comparison
Once you have received an email alert, it will look something like this:
Example of an email notification.