This tutorial supports the original ActivityBot Robot Kit (#32500) and the ActivityBot 360° Robot Kit (#32600). What's the difference?
This kit has High-Speed Continous Rotation Servos + External Encoders. The servo has a white-red-black 3-wire cable. Look for instructions mentioning "external encoders."
This kit has Parallax Feedback 360° High-Speed Servos. This servo has a white-red-black 3-wire cable along with a separate yellow wire for sending feedback signals. It does not use external encoders, as these servos have encoder sensors built right inside the case. Look for instructions mentioning "Feedback 360° servos."
You will use these pieces during the hardware assembly.
You will not need these pieces for the hardware assembly, so you can set them aside and save them for later activities.