what is the ANC switch for on my boat?

[badbass25]

it is on my Nav lights switch.... nav lights (up) and ANC (down) and off (center).... any help appreciated... trying to get boat opperate correctly so i can take it out... thanks...
Wes

[Blue_R70]

"Nav" turns both lights on and is for running. "Anc" is the anchor position and only keeps your rear light on so others can see that you're anchoed.