An illuminated manuscript is like a special book that is decorated in a really fancy way. Imagine you have a special book that you want to make extra special by making the words look really pretty and adding colors and pictures all around the words. That is what someone did a long time ago when they made an illuminated manuscript.
To make an illuminated manuscript, they took a piece of special animal skin called parchment and wrote out the words they wanted to use with a special ink. Then, they decorated the pages with pictures and patterns using bright colors. They used things like gold, silver, or other shiny paints to make the pages extra fancy. Some pictures they drew showed people, animals or places, while others had fancy letters and designs.
It took a lot of time and work to make an illuminated manuscript, but people loved them because they were so beautiful. They were very special because not everyone could read or write, and they were often made just for the wealthy people who could afford them. Today, many illuminated manuscripts are kept in museums so that people can see how beautiful and special they are.