The platforms chart in the TestProject reports lets you see at a glance how your tests are performing across the different platforms they have been run on. This can be very helpful when it comes to seeing which platforms you might need to look into more or for helping to figure out if you have introduced a platform specific bug.
The platform chart can be found by clicking on the middle navigation dot under the charts.
Platform and Distribution Plots Location
These charts are available at the main reports level as a summary view and are also available for each project you have defined