Okay kiddo, so have you ever played with building blocks before? It's kind of like that.
In math and physics, we like to solve problems by breaking them into smaller pieces and figuring out how those pieces fit together. We call this "decomposing" the problem.
An ansatz is kind of like a guess or a blueprint for how we think the pieces of the problem might fit together. It's like when you start building a tower with your blocks, you might have an idea in your head of what it will look like when it's finished. That's your ansatz.
Once we have our guess (our ansatz), we can use math and physics to check and see if it works. If it doesn't, we can adjust our guess and try again. This is kind of like when you build your tower and it falls over - you tweak your design and try again until it stands up on its own!
So an ansatz is just a starting point for solving a problem in math and physics, kind of like a blueprint or a guess. Does that make sense?