Recording Great Audio for Video

What are the benefits of using a microphone on a boom vs a lav vs on the camera? What are the differences between single and dual system recording?

Microphone on a boom is beneficial because it can be completely hidden. On the other hand, a lav is harder to be hidden because it must be attached to the subject. Furthermore, lavs are more likely to create rustling/rubbing sound against the actor's clothing. A boom simply needs to be out of the frame and therefore easier to be kept hidden. A single system is directly plugged into the camera. This way, the audio picked up by the microphone is automatically synced with the recorded video. Dual system recording refers to a system which the microphone is plugged into a digital audio recorder and/or sound mixer. Although this system is requires two or more people, this way can be more beneficial because it allows freedom for the camera.