Bee bread is the fermented pollen of which its outer wall is digested by natural enzymes of bees, allowing all its nutrients available for the human body.

The worker bees digest the pollen and nectar that they collect from the surrounding plant flora through their natural enzymes.

Then they save that digested pollen in the cells of the honeycomb.   The natural enzymes excreted by the bees can digest the outer wall of the pollen, which is called fermentation.  The fermented pollen is now a different product than the pollen itself, and it is called the bee bread.