You may or may not have linked to this page via a review of My Pocket Tai Chi in which I write that the book covers items that this DVD doesn't and, likewise, this DVD is better at explaining the movements as watching is easier then reading instructions.
Dr. Paul Lam takes you through the whole thing, stage by stage, fraction by fraction of each stage. He continually talks to you in a soft voice and is easy to follow.
Having explained a procedure, front-on, with his assistant, he then turns his back to do it again but without you imagining that you are looking into a mirror.
It is extremely useful to see front and rear view at the same time and this is extended into the final chapter where the whole routine is performed. You then have the choice of watching someone facing you, or you can choose to have him with his back to you so that you can copy moves as if you were in a group and you were following the person in front of you.