1. Mutualism: Both organisms benefit from the relationship.

* Example: Bees and flowers. Bees get nectar from the flowers, and in the process, they pollinate the flowers, which helps them reproduce.

2. Commensalism: One organism benefits, and the other is neither harmed nor helped.

* Example: Barnacles on a whale. Barnacles benefit by having a place to live and access to food, while the whale is not affected.

3. Parasitism: One organism benefits, and the other is harmed.

* Example: A tapeworm living in the intestines of a human. The tapeworm benefits by getting food and shelter, while the human is harmed by the tapeworm taking nutrients and potentially causing illness.

It's important to note that there can be gray areas between these categories, and some relationships might fall into multiple categories depending on the specific circumstances.