A skew-hermitian matrix is a special kind of matrix where the numbers inside it follow a certain rule. It is called skew because it is like a mirror image of a regular matrix. Hermitian means that the matrix is symmetrical when you take the "conjugate transpose" of it, which means you switch the rows and columns and also take the complex conjugate of each number.
Now, let's imagine a big square board with a bunch of numbers inside it. These numbers can be real or imaginary, or even a mix of both, but what matters is how they are arranged. If we take this board and flip it like a mirror, we get a new board that looks almost the same, except all the numbers are flipped (like if you were looking at yourself in a mirror). This is what we call a skew matrix.
But a skew-hermitian matrix also has another rule: if we take the conjugate transpose of the matrix, we get the same matrix, but flipped in the other direction (like if you were looking at your reflection in the mirror). This means that the matrix is symmetrical in a special way, and it has some interesting properties when we use it in math.
One way to think about skew-hermitian matrices is to imagine them as rotation matrices. You know how a regular matrix can be used to rotate a point and stretch or compress it in different directions? A skew-hermitian matrix can also do that, but in a different way that's more special. It rotates the point around a certain axis, but it also flips it in a certain way that's hard to explain without getting into more technical details.
Overall, a skew-hermitian matrix is a special kind of matrix that has some interesting symmetrical properties and can be used to rotate and transform points in a special way. It's like a mirror image of a regular matrix, but with some extra rules that make it even cooler.