A digital signal requires a pairing of transmitter and receiver, and can even use authentication to encrypt the signal, meaning you will be limited in how you receive the video from your drone, and the hardware you can use to receive it. For analog signals, things are much simpler. You can think of an analog signal like a radio station, anything in range that can tune to that frequency is able to display the video. Analog signals are very fast, but are often lower resolution, have shorter range, and are prone to interference. Digital signals have higher latency, but also higher resolution, are more reliable, and cost more. A digital signal is the best option if you wish to keep your video private.