You might enjoy Oz and James' Big Wine Adventure, wherein James May learns exactly what you are asking about, while on a very entertaining road trip with a wine

You might enjoy Oz and James' Big Wine Adventure, wherein James May learns exactly what you are asking about, while on a very entertaining road trip with a wine expert (about whom I will not pretend I know anything else). Look up "Oz and James" on YouTube and you'll probably find a few complete episode uploads, if not the whole series.