Evidence-based policy means that decisions made by people in charge (like politicians or government officials) are based on proof or solid information. It's like when you ask your teacher to explain something, and instead of just giving you an opinion, they show you the facts behind their answer.
For example, imagine that a town has a problem with too much garbage in the streets. The mayor wants to try and fix the situation, but they want to make sure they're doing the right thing. So, they collect information like how much garbage people are throwing away, what types of trash bins are most effective, and how much it costs to clean up the trash.
With all this data, the mayor can create a plan that is based on the evidence at hand. This means that they are using solid facts to decide on what action to take, rather than just guessing or going with their gut feeling.
In short, evidence-based policy is all about making informed decisions by gathering information and looking at the facts to figure out what will work best for everyone.