When trying to understand symbiosis it is important to first define what symbiosis is. Symbiosis is a relationship between two organisms that live in close proximity to one another. In some more extreme cases, neither organism is able to survive without the other one. Symbiotic relationships can be defined in three ways. The first type of symbiosis is known as parasitism. In parasitism, only one organism, known as a parasite, benefits, while the other organism, known as the host, is harmed. The second type of relationship is known as commensalism. In commensalism one organism benefits from the relationship while the relationship has no effect on the other organism. The final type of relationship is the focus of this question. Mutualism is the symbiotic relationship in which both organisms benefit from the relationship. Hope this helps!