What the hell is a cuckhold. I don't know English well, explain it to me in a easy way please. Thank you?

A cuckold is the husband of an adulterous wife. In evolutionary biology, the term is also applied to males who are unwittingly investing parental effort in offspring that are not genetically their own.

A man whose woman has had intercourse with another man behind his back. In a longer view it refers to a father that raises some other man's child (through his own wife) in the mistaken belief that the child is his own. Kind of like a variation on a bastard, or perhaps the flip-side to the idea (an illegitimacy in a different sense). In one case (bastard), the child is not acknowledged by his real father and misses out on his inheritance, in the cuckold idea, the father is fooled into passing his property to a non-descendant (an illegitimate offspring, not a true offspring, receives an inheritance he does not deserve).

Historically a cuckold was a man fooled into raising another man's child by his wife. The term comes from the cuckoo, a bird which lays its eggs in the reed warbler's nest fooling the reed warbler that the chick is its own.

In recent times it's become a sub-genre of porn where a man, usually with a small penis (for pornography) watches his partner have sex with other men. There's a huge element of humiliation involved and very often there is a racial element with the pathetic man and his partner being white and the other men being black. The modern cuckold reflects the deeply seated insecurities of a certain kind of man.

In alt-right circles cuck(old) became an insult for (white) men who enjoy equal relationships with their female partners about ten years ago after a break of about 100 years since the last time the word was a serious insult. It's part of their ideology that women should be subservient, so that if a woman is not she must certainly be using her male partner for money and resources while also cheating on him, probably with black men. (It's always racist with the alt-right.) There is no child involved in the insult anymore.

In the last few years the term has been completely shortened to "cuck" and has now become a general insult, though it's only levelled at men and almost exclusively at white men. The people who use the insult are almost exclusively right wing though some will call themselves "libertarians."

a man whose wife cheats on him.

A cuckold is a husband whose wife has met me.