The item you're purchasing has EVERYTHING needed to charge, control, view (FPV), all in one box. You do not need to purchase anything else in order to fly it. For non-beginners, this is usually not necessary.
The item you're purchasing has a built-in receiver with a specific protocol such as ExpressLRS(ELRS), FrSky, Spektrum, Crossfire, etc. and Video Transmitter (VTX). You will be responsible for knowing which protocol is in your radio as well as understanding how to bind the quadcopter/wing to your radio transmitter.
The item you're purchasing requires some things to be installed in order for it to be fully ready. Generally for quadcopter/wings, this is the receiver and/or video transmitter (VTX). You will need to understand that you will likely have to do some sourcing of extra components to make it fully work. Choose the receiver that binds to your radio transmitter, and choose the VTX that aligns with your Goggles / VRX system.
The rawest form. You must build this yourself. Some kits are plug-and-play kits that still require building but have MOST of what you need to make them fly. But in this case, most of the aircraft are requiring still a receiver and/or video transmitter to complete them.