Represents the number of times your application has been launched at any given time by anyone who has your application. Mind you, if your application is portable, thus it doesn't require to actually be installed and it can be sent to anyone, the numbers displayed in this chart can increase significantly.
Please note that it has nothing to do with the number of installs from the Installs view or with any other data from any other view. The data displayed here refers to the installed product, not the installation package.
For example, your application is only installed once by a user on a given machine but it can be launched indefinitely from that point on. This chart can be populated even if the application wasn't installed at all, as long as you have installed the SDK into your application, this view will be populated every time someone opens it.