What is a symbiotic relationship? and how does it work?

Are a special type of  interaction between species

Good morning! ~

There are 2 main different kinds of symbiotic relationships. 

One being; 
A Obligate symbiotic relationship is when 2 animals can not live without each-other. Meaning, they need each-other, or they can't survive. 

And two being;
They choose to be together, they don't -need- each-other per-say, but they want to be together. 

But in general; its a certain relationship between 2 animals. 

If the experiment was perfomed more then once and you get the same results