What does a parasitic relationship mean?

A parasitic relationship is an unbalanced relationship between two or more organisms.

Unlike a symbiotic relationship, where two or more organisms help each other survive, a parasitic organism only benefits on side of the relationship, and sometimes even harms the host, or affected organism.

An example of a symbiotic relationship would be insects that feed on pollen from flowers and, in doing so, cross-pollinate other flowers, helping them to reproduce.

An example of a parasitic relationship would be a tapeworm that resides in the intestines of a human or an animal.

The tapeworm offers no benefit at all to the host, but derives nourishment without giving anything back.