Okay, I'm going to explain KDE to you like you're five.
KDE is like a playground for your computer. When you turn on your computer, there's usually a big blank screen that you can use to do things on your computer like write a letter or draw a picture. KDE is like a giant playground that you can put on that blank screen to make it more fun and colorful.
In the KDE playground, you can do lots of things. There are lots of toys to play with, like a toy called "Dolphin" that helps you find and organize your files, and a toy called "Kate" that lets you write and edit text. There are also lots of games to play, like "Kolf" which is like mini-golf on your computer, and "KMahjongg" which is a fun game where you match tiles with pictures on them.
KDE also lets you change how the playground looks. You can change the colors and the pictures that are on the toys, and you can even change how the whole playground looks. Maybe you'd like it to look like a castle, or maybe like a space station. You get to choose!
Finally, KDE has lots of friends that help it work. There are lots of bees that buzz around and help make things run smoothly, and lots of dragons that help with the fun stuff. And if you ever need help, you can always ask the gnome, who is like a friendly teacher who knows lots of answers.
So that's KDE! It's a fun playground to use on your computer that lets you do lots of things and change how things look.