Large river deltas are important for understanding how rivers behave. They are made up of sediment at the mouth of a river that flows into a sea or lake. Deltas have different parts like subaerial and subaqueous areas, and can be divided into tidal and non-tidal sections. They also have different shapes like delta plain, delta front, and prodelta. Deltas from big rivers can be very complex, with various processes shaping them. The Ganga-Brahmaputra Delta is a good example of a complex delta. Changes in the river, climate, and sea level have influenced how this delta has evolved over time.