A wife is a married woman. "Married" means that the law says two people are legally "joined". During the marriage ceremony, the wife is called the bride.
In countries and times it has been different how many wives a man can have legally. In old times there were no limitations in some countries. In Christianity a man can have one wife. In Islam a man can have up to four wives.
There are some names for special kinds of wives. For example,
a queen is a wife of a king.
A man whose wife is deceased is called a widower.