How to understand Cframe? I never could understand it. I need help because IDK

5,10,3,
1,0,0,
0,1,0,
0,0,1

The first row is the positional vector (1,0,0) is the x vector so the 1 in the second row is xx, 0 is xy, and last 0 digit is xz

I assumed that the x for each letter represent the vector for ? Yes for what? The position? Is the x,y,z the positional number (1,0,0) for the vector x?

What is the second x,y,z variable represent for xx,xy,xz