Modular group

The modular group is like a group of friends. They are all different, but they have a special way of being friends that makes them work well together.

The modular group is made up of special types of numbers called "fractional linear transformations." These are like different kinds of toys that the group can play with.

The modular group has some special rules that they play by when they use these toys. One of the rules is that they can only use the toys that keep the numbers they are playing with between 0 and 1.

Another rule is that they can't have two toys that do the same thing. For example, they can't have two toys that make numbers bigger, because that would be too many of the same type of toy.

Finally, the modular group has a way of combining these toys to make new ones. It's like when you have a bunch of Lego bricks and you can build new things by putting them together in different ways.

Just like friends, the modular group can do different things together. They can solve mathematical problems or create beautiful patterns. But whatever they do, they always follow these special rules to make sure they work well together.