Items on a beehive diagram include the inner and outer covers, the medium super, the brood chamber and the queen excluder. Other items typically found on a beehive diagram are the bottom board and a stand, if one is used.
The outer cover of a beehive provides protection from the elements. The inner cover helps regulate the temperature of the hive by creating voids. The medium super stores excess honey and is where it's harvested. The brood chamber is where the bees live and are raise their young, it's also where they store their food. The queen excluder is literally used to exclude the queen bee and stop her from laying eggs in the wrong chamber. The excluder is only used during honey season. The bottom board helps ventilate the hive and control pests.