If the wife has sex with strangers and the husband knows about it, then it is pure eroticism.
When Cuckolding the husband enjoys the sight of his wife having sex with another man. There are adventures, as the husband may only watch passive. There are stories as he humiliates man as a cuckold.
The wife loves intermarriage intercourse. Often, their sex partners have big and hard cocks. The husband often has only a puny penis. The wife laughs about that.