Poppy seeds are oilseeds  of Poppy flower. There is many different varieties of this flower: white, pink, yellow, orange, red and blue. Also seeds look different, they can vary from almost white through gray, dark gray to dark blue colour.
Poppy seeds that are the most commonly used in baking are from opium poppy (Papaver somniferum). Unripe fruits of the same Poppy are used in production of opium. And as it was proven by Myth Busters (TV program) consumption of bread or cake containing poppy seeds can give false result during drug testing.
They can be used for instance in “Brudas – My Mother’s Poppy Seed Cake” or “Poppy Seed and Maple Syrup Butter Cookies”.