Sons of nobles would serve as a page at around age 7, then become a squire, then knighthood. Knights would begin fighting at ages 16-20. Before becoming a knight you had to have a religious ceremony to be granted knight hood. Knights had education from their fathers also.
Knights were suited in full armor, either chainmail, or plated. Their horses were also fully armored. They had swords and other weapons like jousting sticks. The armor was very expensive and made by a blacksmith.
Knights ate very well because they needed to be fit and healthy for battle. They ate meats, cheeses, breads, wines, fruits and veggies when they were available.