The first two leaves to emerge are called “seed leaves” or “cotyledons." They will usually fall off when they are no longer needed. They are not strictly true leaves but they function as such because they are photosynthetic. The epicotyl emerges from the cotyledons and heads upward as the cotyledons begin photosynthesis. It is the true stem of the plant and tightly furled around it are the first true leaves which begin to unwrap as the stem shoots upward. This is happening on my bean plant:
True leaves begin as a pair of real green leaves that unfurl from the epicotyl after it emerges from the cotyledons. There is one on each side, opposite each other. Subsequent leaves will form as trifoliolates, each leaf will have three leaflets. There is also a top bud on the epicotyl called the apical meristem. It is always hidden in the newest leaf before the leaf unfolds or unwinds from the stem and is the point from which new leaves grow as the plant develops.
True leaves (above and lower photos)