The HUD shows your health bar and the number of bars you have. When you reach zero you will faint and be returned to your dorm.
The Food Sack contains items you collect through your journey. Food in this game contains raw magic, and through magic can be used in many ways.
The Automatic Leveling Bar. This corresponds to your Rank as a student. Higher your rank the higher your level goes up. Certain spells can only be cast on certain levels. You will find in your journey that certain Edibles (creatures in the game) can lower your level.
The Energy Bar creates Energy spheres. In the game powerful moves and magic can be cast that depends on how many are filled. This is filled automatically.