It is the address of the mother's sister or younger sister's husband, usually the elder. In some places, "uncle" is called "aunt father" and "uncle", and in some places, "uncle" is called "aunt son". But "aunt and son" is just a dialect. If you say it in Mandarin, it seems that you are older and will be grandparents.
In fact, there is no difference in essence. Generally refers to the wife's sister's husband, but this title is generally used by relatives, usually between clansmen and in-laws, to describe the relationship between the two sides.
Extended data
China's kinship is extremely complicated. For example, we call my uncle's wife my aunt, my aunt's husband my uncle, my uncle's wife my aunt and my uncle's wife my aunt, but this is not uniform. China is a multi-ethnic country, and the names of each region are slightly different, but this is the general meaning. There is no difference between uncle and uncle in essence, but a title between relatives.
Generally speaking, there may be some differences when introducing peers. For example, this is my son's "Uncle Dog Egg" and this is my wife's "Uncle Cui Hua". The former is used to describe the younger generation and elders, and the latter is used to describe the peers between relatives, but it is not necessary to be so detailed in real life.