explain the term "town air makes free"

"Town air makes a man free" was an expression in mediaeval Europe. In mediaeval Europe, many towns and cities were free from the direct control of the king and the aristocracy. Hence, people in towns were not under feudal rules that constrained their freedom. Instead, they were free to take up any trade or work and live in a much more free manner than people in villages. Hence, it was said that town air makes a man free.