I don’t personally use Bridge, because all of my devices communicate with Node-Red, where all the logic processing is done, and Node-Red then communicates with Blynk.
However, having seen list of Blynk related questions in the past, think a typical scenario is one where you have a temperature sensor connected to one device, a thermostat with a display connected to another, and a relay controlling a heating/cooling device connected to a third device.
The temperature sensor just pushes data in one direction to the thermostat, which is the “master” device.
The relay device needs to be commanded by the thermostat, but may a.so need to send-back information about it’s current status.
The thermostat sits in the middle and takes the data from the temperature sensor, uses information inputted by the user directly (maybe using a physical screen and physical buttons) but also synchronises with app widgets, and pushes temperature and status information out to the app.
The thermostat also commands the relay to turn on or off, and the relay maybe sends back confirmation data about the relay status. The relay device might also have a current sensor attached, to provide feedback about power consumption.
I think the biggest issues/problems that people have with Bridge is that the Sketch Builder example is confusing. It only provides the sketch for one of the devices, and although experienced users can usually work out what needs to be done on the second device from the hints given in the sketch, newcomers find it more difficult.
Once they get into scenarios where data needs to be sent on multiple pins, bi-directional bridging is needed, or bridges between multiple devices are needed then it gets quite difficult to comprehend.
I’m quite a visual person, so for me a diagram explaining how the data flows between various devices would help to make the process make sense, and that’s something that’s lacking at the moment.
I was thinking about writing a guide to this before beta testing began, but I dropped the idea when it became clear that Bridge won’t be used in Blynk 2.0