I don't know what to call it. It's this...feeling. But that sounds too cliche. But aren't cliches there because everyone knows what they mean? They're there because they've been used, and while they might not be sophisticated or eloquent, sometimes you just need to use them.
It's a feeling.
You know when you've known someone for long time, and they understand you completely? They don't need to ask you if you're sad; they can see it in your smile. They could understand everything you wanted to say when you make eye-contact.
That feeling doesn't just happen.
Except today, it did.
So, who knows?