But this begs the question - WHAT even does the term Significant Other Penguin even mean?

The entire term "Significant Other" indicates one Penguin is more significant than other Penguins you might be dating.

In poly situations, WHAT is the difference between your Significant Other Penguin and any other Penguin?

What if you meet a new Penguin who you're more into than you're into your Significant Other Penguin?

What if she meets the same?

Amidst this all, how do you stay sane? And WHERE do you get the time for all this? (Not questioning or ridiculing here but asking out of genuine curiosity. I had once "spun plates" and it was downright exhausting and confusing dating multiple girls)