If there is a task whose label contains 'run' in tasks.json, run button executes that task.
If there is a task whose group.isDefault = true in tasks.json, run button executes that task as a fallback.
If all conditions are not met, the button executes the selected configuretion in launch.json without debugger (You can select a configuretion in debug panel).
Debug button
Debug button executes the selected configuretion in launch.json. Please select a configuretion to spawn via debug panel (You can select a configuretion in debug panel).