"Understanding is defined as a mental grasp; the power of comprehending; especially: the capacity to apprehend general relations to particulars; a superior power of discernment; enlightened intelligence."-Asad Meah
That's a great definition, but it's the word "comprehending" that stands out.
Within the context of a friendship, there's a sense of connection that is a little outside of Mr. Meah's description. He takes a swing at it through his "superior power of discernment" quote, but it's slightly less refined than that explanation.
In short, the best friendships are based on just being able to "get" each other.
Understanding is a foundation for an instinctive and nearly visceral connection with another person, but it is the depth of understanding that makes the friendship a lifelong connection.
And this is where the "Get" appears.
When we "get" another person, we comprehend their peculiarities and we understand their heart. We look past their ego and see the vision within their meaning. They don't confuse us with their anxieties, nor do they disappear into their depression. We see all of them.
We just "get" them.
Agreement with our friends is basic, but doesn't define the "Get." Disagreement and unpredictability, albeit in manageable bites, keeps our attention sharp and our heart open. This is a big part of the "Get." We get happy when they're happy, sad when they're sad. We "get" them, and we travel the same emotional path together.
If you understand what I've just written, you've been there. If you don't, you'll find out. Your love for your friend will transcend your annoyance, impatience, and upset. You won't be bothered or too overly concerned, but still passionate about the welfare of your friend and their feelings. You understand where they're coming from. You can feel their energy in every fashion. Sometimes, you'll get a hunch about them and, when you call, they'll say, "how did you know that?"
That's what "get" means. That's a great part of a good, close friendship.