I'm teaching myself matrices because it could prove useful in the future.

I'll just run through a few things I've done to check if I'm correct:

i'm confident in adding/subtracting and multiplying.

What I'm having trouble getting my mind around is identities, inverses and determinants for 2x2 matrices.

In my book it says that for matrices of a given dimension (2x2) a identityIexists...

What does thisImean?

Then after this it says

If

I have no idea in the world what this means. Could someone clarify it for me please =]

Thanks in advanced!