Symbiosis is when two organisms work together in one of three ways
1: parasitism- when one animal is benefited and the other is being harmed such as a flea on a dog
2: commensalism- when one animal as benefited and the other is neither harmed nor benefited, such as a bird nest in a tree
3: mutualism- when both animals work together and benefit, like a crocodile and a crocodile bird (the crocodile bird goes into the crocodiles mouth and eats the leftover food and flies away unharmed)