Punt!

Okay, we know what the bottle shapes mean, now let's find out about that indention in the bottom of most bottles. Does it have anything to do with the quality of the wine? Not according to Wikipedia!

Punts
A punt, also known as a kick-up, refers to the dimple at the bottom of a wine bottle. There is no consensus explanation for its purpose. The more commonly cited explanations include:

• it is a historical remnant from the era when wine bottles were free blown using a blowpipe and pontil. This technique leaves a punt mark on the base of the bottle; by indenting the point where the pontil is attached, this scar would not scratch the table or make the bottle unstable.
• it had the function of making the bottle less likely to topple over -- a bottle designed with a flat bottom only needs a small imperfection to make it unstable -- the dimple historically allowed for a larger margin of error
• it consolidates sediment deposits in a thick ring at the bottom of the bottle, preventing it from being poured into the glass
• it increases the strength of the bottle, allowing it to hold the high pressure of sparkling wine/champagne
• it holds the bottles in place on pegs of a conveyor belt as they go through the filling process in manufacturing plants
• it accommodates the pourer's thumb for stability and ease of pouring
• According to legend the punt was used by servants. They often knew more than their master about what was happening in town, and with a thumb up the punt they could show their master whether a guest was reliable or not.
• it provides a grip for riddling a bottle of sparkling wine manually in the traditional champagne production process.
• it simply takes up some of the volume of the bottle, giving the impression that you're getting more wine for your money than is actually the case
• Taverns had a steel pin set vertically in the bar. The empty bottle would be thrust bottom-end down onto this pin, puncturing a hole in the top of the punt, guaranteeing the bottle could not be refilled [folklore].
• The punt acts as a lens, refracting the light to make the color of the wine more appealing.
• Prevents the bottle from resonating as easily, decreasing the likelihood of shattering during transportation.
• Allows bottles to be more easily stacked end to end.

compiled from internet sources to include wikipedia