A symbiotic relationship is a close and often long-term interaction between two different biological species, which can benefit one or both parties involved. There are various types of symbiosis, including mutualism, where both organisms benefit; commensalism, where one benefits and the other is unaffected; and parasitism, in which one species benefits at the expense of the other. These interactions are essential for ecosystem dynamics, influencing species survival, nutrient cycling, and biodiversity.