What does symbiosis mean?
The word itself means "living together".
Textbooks use the de Bary definition and this is: symbiosis = all species interactions.
Some symbiotic relationships are obligate, meaning that both symbionts entirely depend on each other for survival and cannot live on their own.
Others are facultative, meaning that they can, but do not have to live with the other organism.
Symbiotic relationships include those associations in which one organism lives on another (ectosymbiosis), or where one partner lives inside the other (endosymbiosis).
There is much more terminology when this is further divided into parasitic, commensal and mutualist relationships.