Help identify purpose for holes in window frame

The panel is part of the venting system for the refrigerator. There should be another vent near or on the roof of your trailer. Fresh air is pulled through here and exhausted out of the top. If you remove this panel then you can access the backside of the refrigerator to get to things like the burner and electrical connections. To remove it, give the tabs a quarter turn with a flat head screwdriver or coin. Sometimes the panels just pop off and snap into place. It's a good idea to line the backside of the vent with window screening material to prevent critters from going in there and making a home.