The wireless diagnostics section gives you the insights into your Wi-Fi environment.
Client Table shows you a list of devices connected to your Wi-Fi.
AP Scan gives you insights into the access points around you.
Client Diagnostics gives you Wi-Fi data specific to each device that is connected to your Wi-Fi. This is helpful when you have one Wi-Fi device that is having problems.
Channel Analysis gives you Wi-Fi data about each channel like non-Wi-Fi noise, noise from other access points, total channel noise, and channel rank.