Young sunflowers follow the sun from east to west through the day. It's called heliotropism and can improve photosynthesis by 10%.
Once they get older they stop moving, but they always settle on facing east to better absorb heat from the morning sun.
The large flower head is a pseudanthium or false flower. In truth, sunflowers are an inflorescence, a compact collection of many smaller flowers. These are recognizable as the fuzzy center. Each of these tiny flowers become individual sunflower seeds.