GSC: This is referred to Ground Control Station. GCS can be Andruav App running in GCS mode, WebClient or applications such as Mission Planner and QGroundControl.
Drone Mode: The mobile that is mounted on the drone should run in Drone-Mode. This is important to be able to communicate with flying control boards, capture images and all other information.
FCB: Flight Control Board; This is PixHawk or simillar boards that run Ardupilot firmware.
Pin Code: An alphanumeric text that uniquely identify your Andruav app on a particular mobile. This number never changes, unless you remove and reinstall Andruav on the device again. This number is not editable as well.
Access Code: Access code is a password generated by the system, that is used with your email account to authenticate your device on Andruav Server. Sharing your access code with other persons will allow them to join their devices on you Andruav account. This is useful when you want your friend enter as a GCS and share with you your flight.
DroneKit: This is a library developed by 3DR that make connection with PixHawk, APM, SOLO and virtually any board that supports MAVLINK more reliable.