A fuzzy number is like a regular number, but with a bit of fuzziness around it. Imagine you have a number line and you want to put a dot on it to represent a number. A regular number would be a very precise dot that you could say exactly where it is. But a fuzzy number would be a dot that is a bit blurry and could be in a few different places, but not too far away from where you think it should be.
For example, imagine you want to represent how tall you are on a number line. A regular number would be something like "I am exactly 4 feet tall." But a fuzzy number could be something like "I am between 3.5 and 4.5 feet tall." That way, even if you're not exactly 4 feet tall, you're still close enough to count as being in that range.
Fuzzy numbers are used a lot in things like mathematics and engineering where you might not have precise data, but you still want to make estimates or predictions. By using fuzzy numbers, you can still get a pretty good idea of what's going on even if you don't have all the details.