The convention on the political rights of women is like a set of rules that says that women should be allowed to take part in making decisions in their country, just like men. It's like playing a game of soccer, where everyone follows the same rules and has the same chance to score a goal.
In some countries, women are not allowed to vote or to be elected as leaders. This convention says that they should have the right to do those things, because everyone should have a say in how their country is run.
This convention was made to help people understand that women are just as important as men, and that they can do anything that men can do. It's like when your mom tells you that you can be anything you want to be when you grow up, even if you're a girl.
So, the convention on the political rights of women is like a big sign that says "Girls can do anything and make their own decisions, just like boys."