It ties the Dante I/O card’s “control port” to the console’s built in network ports. This doesn’t pass Dante audio, but it does allow you to plug the console into a regular network that includes a computer that you wish to run Dante controller on. Prior to this being an option, you would physically have to connect the control port on the Dante card to the built in network port on the console to get this functionality. Now it does it internally so you don’t have to physically patch this anymore.
Of course there are many times when you don’t want to connect the Dante I/O card to the network your console is on. Personally I like to keep my Dante network completely separate when I can (because it ends up being more reliable and easier to troubleshoot if there is a problem), so I generally don’t want to turn the internal bridge option on. If I need to use Dante Controller software, I plug the computer into the Dante card’s network, not the network the console is on.
Long story short, I personally would recommend that you leave it turned off unless you have a specific use case that requires that it be turned on.