Wetlands is a general term for places that can look quite different depending on their formation. There are fens, bogs, potholes, swamps, and marshes that are fresh water, brackish, and salt water. Part of the distinction of these many kinds of wetland is what conditions make them. Some form where there is a constant moving source of water, so latitude and salinity of the water determine which plant species grow. Others have a closed system, depending on precipitation or ground water, so latitude, pH of the water, and amount and frequency of flooding determine what species grow.
What follows are some general definitions from Our Nation’s Wetlands, EPA Wetland Fact Sheet Series, Bogs of the Northeast, and Waterlogged Wealth. There are further delineations within these groups, for instance marshes can be characterized further as emergent, low marsh, and high marsh. Swamps can be emergent, shrub, or forested. In many of these wetland types mud flats form part of the transition from one habitat type to another. These may or may not be considered wetlands depending on the need for a definition. Mudflats may have only algae for vegetation, so if plant type is used to define a wetland they might be considered a wetland, or part of deep water habitat.
What is important is to see how many faces water, soil, and plants can put on wetlands.