A visualization library is like a big box of Legos that helps us build pretty pictures from data. Think about how you can use Legos to build a cool spaceship or castle - it's not just about the individual pieces, but how you put them together to make something neat.
Similarly, a visualization library helps us take data - like numbers or words - and turn it into graphs or charts that make it easier to understand. For example, let's say we have a lot of data about how many ice cream cones people in different cities are buying. We could make a graph with different colors and bars that show us which city buys the most ice cream, or which is growing the fastest.
The cool thing about a visualization library is that it gives us lots of different tools to work with, from simple bar charts and pie graphs to really complex diagrams that might show relationships between lots of different variables. No matter what kind of picture we want to make, the library has all the Legos we need to build it, and it does a lot of the hard work for us so we don't have to start from scratch every time we want to make something.