Currently Online 
It's just a metric for retailers to use when they're deciding what to order and how much. It's an industry reference and was never really intended to be anything more. It lets you know what kind of sale-through and marketing support you can expect at a minimum. Distributors send you monthly order catalogs with EVERY game being released in the near future and the "A" designations are just there to help sort through the crap.
Believe me, when the Wii was sailing along, there was a LOT of shovelware to sift through. It's a very handy tool. One thing I noticed when I used to be in charge of purchasing is that the distributor reps typically had very little first-hand information about games and would have to look up projections, whereas they were mostly familiar with all the video releases.
