A mussel is a type of bivalve mollusk that lives in both freshwater and saltwater environments. They have a two-part shell that is usually dark blue, black, or brown, and they attach themselves to rocks, piers, or other surfaces using strong threads called byssal threads. Mussels are filter feeders, meaning they obtain their food by filtering plankton and other small particles from the water. Mussels are an important part of many ecosystems, as they help improve water quality by filtering out pollutants. They are also a popular food source in various cuisines around the world, often prepared in dishes like moules marinières or served with pasta. Additionally, mussels are cultivated in aquaculture, providing a sustainable seafood option.