When you open the GCS for the first time, you will see that it is organized into tabs and pages for easy navigation. 

Welcome Tab:

 The greeting tab which shows you the latest project information and activity, provides buttons for the other pages, as well as containing the start button for the Vehicle Setup Wizard. 

Flight Data Tab

Displays live data from the flight controller. Display useful information about flight controller status like alarms in SystemHealth.

Configuration Tab

This tab contains sub pages which enable you to configure major elements of the flight controller using simple graphical interfaces.
None of the sub pages are active unless a flight controller is connected to GCS.

System

A configurable interface for viewing and modifying advanced settings, live data, GPS data and more.

Scopes

Real-time graphing of flight controller data.  Care should be taken to not let auto-scaling fool you into thinking you have a problem where there is none.
The longer a scope is functioning, the tighter the scale may get, and a very small deviation in a value may look significant when it's not.

HITL

An interface for the GCS to act as a bridge between a flight simulator, and either actual hardware running through the telemetry link or simulated hardware running on the computer.

Firmware: Inspect the current firmware version, and upgrade the bootloader/firmware of the flight controller.