What were the concubines of ancient generals like? What will they do?

In the ancient society of China, where men were superior to women, the system of three wives and four concubines was practiced, that is, polygamy. More precisely, it is monogamy and concubinage. In ancient China, etiquette was very important, so the wife stood in the dominant position, and the rest were concubines. Concubine should respect the eldest lady, so the so-called rivalry in those TV dramas is a joke.