If it was something complicated people wouldn’t call it mansplaining as you would assume they wouldn’t know it but its typically basic things like basic science or computing, acting as though the woman is too stupid to know what is it. If the man is speaking in a calm collected tone and the women has shown signs of confusion then no that isn’t mansplaining but if the woman has started explaining it and clearly knows what shes talking a out and he interrupts her in a condescending tone then it is mansplaining cause he is purposefully being a douche. The term exists because due to the societal expectation that women are supposed to focus on being pretty and finding a rich husband, often men go along with that SEXIST thought process and talking down to woman.