What is a ladder in machine knitting?

A ladder is a column of enlarged sinker loops formed by the yarn that floats across the space between two working needles when there are one or more non-working needles between them.

A Needle out of work will create a bar that is the width of one stitch; done over several rows these bars look like the rungs of a ladder. A very simple technique that I have done innumerable times and never thought very much about. I realized I had more to learn about ladders.