Symbiosis

Mutualism is when two animals benefit from each other. A deer in a forest provides food for birds with the bugs on it's back, and the bird cleans it. They help each other out.

Commensalism is when one animal benifits off of another, and the other isn't really affected. Many sloths have little partials in their fur, that don't really harm them in any way, and maquitos come aroud and eat off of their back. This doesn't really help of harm the sloth, but the masquito gets a meal.

Parasiism is when one animal benifits, and the other is harmed. Humans aren't really good for forrests as we often cut down these trees causing them to die... and we get wood... awesome.