Okay, so you know how some countries have kings and queens, right? Well, in England, they have a queen named Queen Elizabeth II. She's been the queen for a really long time, since 1952, in fact! But one day, she'll need to retire or pass away, and when that happens, someone else will become the king or queen of England.
Now, in the past, only boys could become king, even if they had an older sister. This was called "male primogeniture," which is a fancy way of saying that only boys could inherit the throne. But in 2015, England changed that rule with something called the Succession to the Crown Act.
What the Succession to the Crown Act did was change the rule so that girls can become queen too, even if they have a younger brother. So if Queen Elizabeth II passes away or retires, her son Prince Charles would become king. And if Prince Charles passes away or retires, his oldest child Prince William would become king, instead of his younger brother Prince Harry.
This is a big deal because it means that girls have the same chance as boys to become king or queen, and it's important to make sure that everyone is treated fairly and can have the same opportunities in life.