Once upon a time, there were three big states in India called Madras, Mysore, and Andhra Pradesh. But people weren't happy because Madras and Mysore were bigger and had more power than Andhra Pradesh.
So, the leaders of Andhra Pradesh and the leaders of India had a discussion and decided to make Andhra Pradesh smaller and give some of its land to Madras and some to Mysore. This would make them all more equal and happy.
But there was a problem. Madras and Mysore were worried that people from Andhra Pradesh would come to their states and take jobs and homes away from the locals. So, they made a promise or an agreement with the leaders of Andhra Pradesh that they would not let people from Andhra Pradesh migrate to their states.
This promise or agreement is called a gentlemen's agreement because they didn't write it down, and it was just a verbal promise between the leaders. Because of this agreement, people from Andhra Pradesh could not go to Madras or Mysore easily, and this made life very hard for them.
Eventually, the Indian government realized that this agreement was causing problems and unfairness, so they made a new law that allowed people from Andhra Pradesh to migrate to other states in India. This was called the Andhra Pradesh Reorganization Act, and it was passed in 2014, many years after the gentlemen's agreement.
So, even though the gentlemen's agreement caused hardship for people from Andhra Pradesh, it taught us all an important lesson about being fair and treating others equally, no matter where they come from.