Mutualism describes the ecological interaction between two or more species where each species has a net benefit. Mutualism is a common type of ecological interaction. Prominent examples are:the nutrient exchange between vascular plants and mycorrhizal fungi, the fertilization of flowering plants by pollinators, the ways plants use fruits and edible seeds to encourage animal aid in seed dispersal, and the way corals become photosynthetic with the help of the microorganism zooxanthellae.

In ecology, a biological interaction is the effect that a pair of organisms living together in a community have on each other. They can be either of the same species, or of different species. These effects may be short-term, or long-term, both often strongly influence the adaptation and evolution of the species involved. Biological interactions range from mutualism, beneficial to both partners, to competition, harmful to both partners. Interactions can be direct when physical contact is established or indirect, through intermediaries such as shared resources, territories, ecological services, metabolic waste, toxins or growth inhibitors. This type of relationship can be shown by net effect based on individual effects on both organisms arising out of relationship.