I've heard my friends' kids using the phrase "bruh moment" too, and from what I gather, it's basically an expression of shock, surprise, or embarrassment, similar to saying "oh man" or "wow". They usually use it when something crazy or unexpected happens, like a funny video or a plot twist in a game, and they're trying to convey that they can't believe what just happened. It's often used in a lighthearted or humorous way, and it's not typically meant to be taken seriously. I think it's cool that you're trying to stay up to date with modern slang, it'll definitely help you connect with your child better.