Didactics is just a big, fancy word for the way teachers teach things to students. It's important because it helps students learn and understand things better.
Imagine you have a toy you've never played with before. If someone just handed it to you, you might not know what it does or how to play with it. But if someone showed you how to play with it and told you what it does, you would have a much better time playing with it!
The same thing goes for school. Teachers use different techniques and methods to help students learn and understand material. Some teachers might use drawings or pictures to help explain things, while others might ask students questions or have them read a story.
By using good didactics, teachers can help their students learn and remember things more easily. It's a really important part of being a good teacher!