Quesions on beer gravity

Some brewers put the gravity of a beer on the bottle more to cater to homebrewers than anything. It's a measurement of residual sugars that represent the ABV of the beer based on how much of the sugars it started with after turned into wort (unfermented beer) versus the remaining sugars after the yeast go to work on the wort. For the beer drinker, it's not really a critical piece of information IMO. The gravity doesn't necessarily affect the freshness of a beer, but beers that are higher in ABV and use darker malts do have a higher tendency to resist oxidation than those lighter in ABV or that utilize lighter malts.

 

Gravity readings typically are not on a beer's label, but you can sometimes find them on the brewery's website with the description of the beer. Like @FinchSCF says, these readings are essentially meaningless to the typical beer drinker. The ABV of a beer is more readily available than any other technical data about a beer; however, if you know the Original Gravity and the Final Gravity readings but not the ABV, there are a couple of formulas that can be used to calculate the approximate ABV. (OG - FG) * 131.25 = ABV or ((OG - FG) * 1000/7.46) + 0.2 = ABV

A rough rule of thumb for aging beers is that malty beers that are 8% ABV or higher can easily be aged. Beers that are hop forward will suffer from hop degradation with age, but they won't spoil. Exceptions exist to the 8% aging rule, like sours, lambics, etc.

 

As others stated, OG is the main driver of how high the ABV is, but the FG will also tell you how "sweet" or "dry" a beer will taste, and the amount of body. For example, your typical saison will have a low FG (thin and dry), and typical oatmeal stout will have a higher FG (thicker and sweeter).

Freshness has more to do with the initial flavor profile, to determine whether a beer is likely to maintain that flavor longer. Also, the quality control during brewing and packaging.