Matrix
A grid of numbers that moves, turns or scales every point in one step.
See it in Fractal mirror. Change Rotation under Transform and watch every part of the picture turn together.
In plain words
A matrix is a small table of numbers, such as two rows by two columns. Multiply a point by it, and out comes a new point. One matrix can turn, stretch, shrink or flip every point the same way. Several matrices can be multiplied into one, so a whole chain of moves costs one step. That is why 3D graphics lean on them so heavily.