You will have access to different monitoring page like Overview, by Networks, etc... and more will come during the Beta.
The performance chart will help to have a quick access to a metric (transactions, revenues, etc...) and allow you to compare with a previous time range :
For this example, today it's the 20th January, the revenue for this month (January) is 39.26 EUR. From the 1st to 20th December the revenue was 34.97 EUR, your performance is 12.27% better than the previous month.
The total December revenue was 52.35 EUR, you can see with the chart if you have reached the previous month revenue.
Here is an example with worse performance than the previous month :