I have a friend I can talk to about "anything". That's a good thing generally, it helps to talk over worries and relationship issues with someone not directly involved.
My friend has recently shared some things about his marriage that I know I wouldn't be happy if DH was telling another woman, ut I'd be pleased if he was seeking help from a male friend. The kinds of things I might talk to my closest female friend or my sister about.
It was very much "I don't know how to fix this" rather than things would be better if I was with you, which has never, ever happened, but it still makes me a bit uncomfortable to think about how his DW would feel if she knew.
We first became friends when we worked together in an all male environment and he seemed like the "safe" one because he was such a devoted husband and father, but I'm aware they've had some rocky times recently, which I'm certain are nothing to do with me, but I don't want to become part of the problem.
What is the difference with sharing feelings in the way I would with my BFF or my sister and an emotional affair?