So, there is something called a Projective Special Unitary Group. It sounds super fancy, but we can break it down to make it easier to understand.
First, let's look at what a group is. A group is like a club where there are some rules that everyone has to follow. In math, a group has things called elements that all follow certain rules.
Next, let's talk about what "unitary" means. In math, unitary means that something is special and has specific properties. In this case, we are talking about matrices. Matrices are like big boxes of numbers that we use in math. Unitary matrices have special properties when we multiply them together, which makes them super useful.
Now, we can talk about the "special" part of Projective Special Unitary Group. This just means that the group has some extra special properties that make it different from other unitary groups.
Finally, we can talk about the "projective" part. This means that there is something called "projective equivalence" that this group follows. It's a bit complicated, but basically it means that even if two elements look different, they are actually the same if you look at them in a certain way.
So, all together, the Projective Special Unitary Group is like a club of special matrices that follow some very specific rules to make them even more special. And even if two matrices look different, they might actually be the same if you look at them in a special way.