finding the matrix info on a text frame?

I wanted to understand the matrix values and methods so I could make a script to select or not select textframes that are angled.

Can anyone explain this matrix stuff to me?

This script is the only example I have found so far.

if ( app.documents.length > 0 ) {

var moveMatrix = app.getIdentityMatrix( 0.5, 1.5 );

var totalMatrix = concatenateRotationMatrix( moveMatrix, 10 );

var doc = app.activeDocument.activeLayer;

for ( i = 0; i < doc.pageItems.length; i++ ) {

doc.pageItems[i].transform( totalMatrix );

}

}

Im thinking I need to use getRotationMatrix([angle])

any help would be greatly appreciated,

Duane