My friend is divorced. That means his marriage was terminated and the bonds of matrimony dissolved.
Why did they get divorced?
They had a personality clash which led to many arguments. They both decided it was better to become independent of each other.
That is probably best, when you cannot get a long, that tends to happen.
In many countries monogamy is required by law so divorce allows them to marry other people. In the US it isn't as important for that reason.