This handy contraption is quite versatile. In the winter it can be put right-side up and filled with wood chips (see picture below) this acts as insulation, and in the summer you can flip it over without the wood chips and it will ventilate your hive to help reduce overheating.
This is in the winter position, in summer you dump out the wood chips and flip the box over, putting the inner cover on top of it instead of below it. See Hive Parts for more details on this entire subject or click a link here to find out more about a specific part: Outer Cover (specifically a telescoping top in this picture), Inner Cover, Boxes (Brood chamber and honey super together), Bottom Board (specifically a screen bottom board in this picture).