Square matrices are used (in computer graphics) to represent geometric transformations.
If you sometimes forget whether rows or columns come first, just remember that matrices are build out of rowman columns.
A matrix can be given a name. In printed text, the name for a matrix is usually a capital letter in bold face, like A or M. Sometimes as a reminder the dimensions are written to the right of the letter, as in B3x3.
The elements of a matrix also have names, usually a lower-case letter the same as the matrix name, with the position of the element written as a subscript. So, for example, the 3x3 matrix A might be written as:
Sometimes you write A = [aij] to say that the elements of matrix A are named aij.
(Thought Question:) If two matrices contain the same values, but in different locations, are the matrices equal?