Chablis is one of the two most-renowned regions for Chardonnay in Burgundy. As you can see on a map, Chablis is actually a fairly distinct appellation, falling to the northwest of the main northerly track of the rest of the appellations of the district.
Chablis is produced exclusively from the Chardonnay grape. It gets its classic Chablis profile -- lean, flinty, and almost steely with bright citrus-tinged fruit flavors -- primarily from the soil in which the vines grow. Known as kimmeridgian, this clay-rich soil is rich with chalk and fossilized oyster shells.
The winemaking style in Chablis is generally quite neutral, with the use of new oak barrel quite limited, resulting in vibrant wines that can be lean and firm in their youth but can age quite well due to their firm acidity.
Map courtesy of Kobrand