Mutualism, parasitism, and commensalism

Mutualism: 

This is a beneficial relationship to both partners of different species living together. For example a bee and a pollinating flower. The bee gains nectar from the flower for survival, as it uses the bee to carry its pollen to other flowers. So both organisms living together benefit from their existence.
Parasitism: 

Parasites are completely dependent on a host for survival. The relationship is beneficial to one, and harmful to the other.  Parasites may live outside or inside a host; they are called ectoparasites (the prefix ecto means outside) and endoparasites (the prefix endo means inside). An example of the endoparasite is the tapeworms which live in the digestive systems of its host. Examples of ectoparasites are ticks and lice.
Commensalism: 

The association of two or more partners living together, where only one benefits from the partnership and the other remains unharmed.  An example of this is the relationship between a sea anemone with and a clown fish. The anemone travels with the fish on route to its destination and the fish remains unharmed.