SmartThings could natively support the ability for devices on the LAN (e.g. cameras or
Blue Iris) to talk back and forth. But for the sake of security, they try to prevent Edge drivers having that ability.
The Edge Bridge is a community member's workaround for that and I think it works pretty well. The main thing it does is maintain the connection to the ST hub so that if the internal port number changes, the bridge knows about it. It's finicky to set up, but it's been pretty stable since.
Note: Edge Bridge can enable other functionality beyond allowing BI to activate a virtual motion sensor. I suggest reading up more on it.
