Open philanthropy is like when you have extra toys and you want to give them to other kids who don't have as many toys as you. Except instead of toys, it's about giving money to people who are trying to make the world a better place.
Now, when you give money to people or organizations, you want to make sure that they're going to use the money in the best way possible. So, what you can do is ask them questions and do some research to find out what they plan to do with the money, how they're going to do it, and what the results might be.
Open philanthropy is when you share all of this information with other people, so that they can also decide if they want to help out. It's like a big group of people getting together and saying, "Okay, we all want to help make the world a better place. Let's work together to make sure that we're using our money in the best way possible."
So instead of just giving money to anyone who asks, it's like a bunch of grown-ups get together and ask a lot of questions and make extra sure that the money will go where it's needed most. They all share what they find out, so everyone can decide together what to do.