The idiom comes from the example of eating something. When you eat a meal, you cannot eat it all in one mouthful. You take small bites and eventually eat the entire meal. When you are learning something, you cannot learn all of it in one instant. You learn small portions of it until you have learned it all. Those small portions are referred to sometimes as, "Learning Bites". "Mary learned algebra in her sophomore year of high school. Every school day, she was given small learning bites to accomplish that task."

This seems to be a playful pun. Bites refers to biting food or something you could eat. Yet it also refers to small pieces of something. It is a play on words that probably means small portions of learning. 'Learning Bites'. I hope this helps. Mat