what is it

That switch is used for the ceiling lights, when the bed above the captains chairs is in the down position. So the person sleeping up there does not have to get down to shut off the lights.

:)

Ok the lite does not turn on when pushed?the switch does not stay pushed in when pushed it springs back to the same position it just rocks back to original position
It’s not tv booster

Well two good guesses up there
1: OTA antenna amplifier.. If you do not have either a matrix switch (Box of many buttons) with a POWER button. or a wall plate with teh 12 volt outlet, antenna connection, switch and light. or a Sensar Pro. that's a good chance.

2: Satellite antenna (rooftop dome) you will have a Dome up there.
The lack of "Winegard" on the switch suggests a dome.

I'm guessing it's for the satellite. If you turn the switch on you should hear the satellite move.

It could be the amplifier for your over the air TV.