The Montevideo Convention is a set of rules that countries follow to become official countries. In order to become an official country, a place needs to meet four important requirements:
1. It needs to have its own government
2. It needs to have a defined territory with fixed borders
3. It needs to have a population of people who live in that territory
4. It needs to have the ability to interact with other countries and governments.
If a place meets all of these requirements, then other countries will recognize it as a separate and independent country. These rules were made a long time ago by many countries and are known as the Montevideo Convention. They are like a set of rules that everyone agrees to so that everyone knows who is a country and who isn't. Think of it like a game of soccer where everyone follows the same rules so that the game is fair and everyone knows how to play.