Tannin:
A compound found in the skins and stems of grapes and some other plants. It acts as a preservative, and is an important component in the balance of any red wine. It's astringent -- when it's out of balance, its effect on your mouth is similar to that of strong, black tea or aspirin.

Acid:
An essential component for any balanced wine. The fruit-acid balance in wine is sort of like the fat-acid balance in a vinaigrette dressing.

Thin:
Thin wines are ones that are light in body, like skim milk. Full wines are more like half and half.

Cru:
The word "cru" means growth; in this context, "premier cru" means "first growth."