This means Apple and your local Apple Store have older models in inventory they need to move quickly. If you are looking for a new Mac and don't mind the previous generation (they are so "this past Tuesday"), you can get some pretty good deals. We have seen up to $600 off the original price on some models.
Take a look at the clearance area of Apple's web site to see what is currently availabe. Also, if you can manage the time, I would suggest a trip to the nearest Apple store, they may have deals that are better than the ones on the web.
Lastly, if you just purchased a new Mac (in the last 14 days) you should should contact Apple regarding their price protection plan. Here is a snippet from the web site to save an extra click or two...
Should Apple reduce its price on any shipped product within 14 calendar days of shipment, you may contact Apple Sales Support at 1-800-676-2775 to request a refund or credit of the difference between the price you were charged and the current selling price. To receive the refund or credit you must contact Apple within 14 calendar days of the price change.