Java grammatical evolution is like playing a game where you make sentences with specific rules, but instead of words, you use computer code.
To start, you give the game a task to solve, like finding the best route to take on a map. The game then creates a bunch of sentences using the rules you gave it, but the sentences are really just computer code.
The game then runs the code to see how well it solves the task. If the code does a good job, it gets to stay and the game makes more sentences based on it. If the code does badly, it gets thrown out and the game starts fresh.
Over time, the game gets better and better at making code that solves the task. Eventually, it might even find the best possible solution!
It's like teaching a robot how to do a task by giving it lots of examples and feedback until it gets really good at it.