How can I get a quick overview of my executed tests?

In some interactive dashboards:

There are several ways to get such information. The easiest one is to use the Test Execution Overview dashboard available in the Tools tab or via a selected folder in the design tree:

Inside a report:

MatrixALM and MatrixQMS come also with a standard set of predefined reports that allow you to get an overview of the current status of the project.

One of these reports is the Test Execution Summary which gives an overview of the status of test execution.

This report is available in the REPORT section of the Tools tab: