A more thorough explanation:

A morganatic marriage is a type of marriage where a man of higher social status marries a woman of lower social status, and the wife and her children have no claims to the husband's title or possessions. This type of marriage is now limited to royal marriages.

For example, in the past, a prince might marry a commoner in a morganatic marriage. The prince would keep his title and possessions, but his wife and children would not have any claim to them.

This type of marriage is also known as a left-handed marriage or a salic marriage.