What is the difference between COM and Auxilary COM signals?
That frequency range is not for navigation equipment at all, so I would speculate that it isn't related to the navigation system.

They don't receive two types of signals; they do the exact same thing, but the reason someone may want two radios is to make things easier during flight.

What I think you are seeing is your primary communications radio system, and then a switch for an additional, optional "Com 2" unit that may or may not be installed in the aircraft.

Let's say you are talking to air traffic control, and you want to listen to an automated weather station without having to leave the ATC frequency; most systems provide you with an option to listen to both Com 1 and Com 2 at the same time, while allowing you to transmit on only one of them.  That way, you could monitor and talk on ATC's frequency on Com 1 while getting a weather update on Com 2.

Another advantage is that you can transition between frequencies faster by simply changing from Com 1 to Com 2 (ie. "AUX COM") after having already set the frequency you want to switch to in the other Com.

Yet another advantage is that one com will act as a backup to the other if either one stops working for some reason.