Cotyledons are the first leaves that appear on a seedling after germination. They are part of the seed and provide essential nutrients to the developing plant until true leaves can grow. Cotyledons can vary in shape and size depending on the type of plant, and they play a crucial role in the early stages of growth. In botanical terms, plants are classified as either monocots or dicots based on the number of cotyledons they have. Monocots have one cotyledon, while dicots have two. This classification helps in identifying and studying different plant species and their characteristics.