What is an aroma?
An aroma is an emanation exuded by certain substances, either vegetal (flowers, fruits) or animal (amber, musk). It is a smell, a scent.
An aroma's molecules belong to various chemical families, including alcohols, aldehydes, ketones, acids, and esters.
The world of aromas is wide and varied, and in order to set down an orderly groundwork, œnologists have developed systems for classifying them. Thus, aromas and smells are commonly categorized into these broad groups:

• Flowers
• Fresh fruits
• Dried and stewed fruits
• Vegetation and underbrush
• Woody notes
• Spices and aromatic herbs
• Balsamics
• Animal notes
• Minerals
• Roasted, torrified notes

Going back to the source: a bunch of grapes
A bunch of grapes is made up of a cluster of small berries which together form a whole.
Each individual grape is made up of:

• A membrane: the skin
• Flesh: the pulp
• Seeds: the pips

The skin is the part of the grape that contains its aromatic substances, as well as the pigmented matter and tannins. Only grapes of the Muscat variety contain pigment and tannins in their pulp.
Indeed, each variety has specific aromatic characteristics, which are in turn passed on to the wine.
A wine's aromas vary in intensity and finesse, depending on:

• Climate (cold, heat, aridity…)
• Terroir, parcel
• The grapes' maturity level
• Volume of production, crop yield

Last but not least: in wine
Wine contains many volatile compounds, which can be observed in two ways:

• Through the nasal passages, via the nose: smell
• Through retro-olfaction, via the mouth: aroma

Aromas transmitted by the fruit, or the grape variety, are called primary.
Aromas produced by fermentation are called secondary.
A wine's aromatic characteristics change with age and can go, for example:
   from Flowers, Fresh Fruits → Vegetal, Dried Fruits → to Animal
In Chardonnay
Having most likely originated in Burgundy, this white variety is popular throughout the world because it has good aromatic potential and adapts easily to different climates.
However, in Burgundy, as in most French wine regions, when tasting, the terroir (Chassagne-Montrachet, Meursault) and specific appellation are more important criteria than the grape variety.
Chardonnay's main aromas as found in the white wines of Burgundy are nicely shown by a poster put out by the Bureau Interprofessionel des Vins de Bourgogne, which you can download here.
In Pinot Noir
Also graced with great aromatic complexity, this red variety is more demanding in its growing conditions. It can only flourish in temperate climates and in very specific types of soil.
However, in Burgundy, as in most French wine regions, when tasting, the terroir (Chassagne-Montrachet, Volnay) and specific appellation are more important criteria than the grape variety.
In 1395, Philip the Bold, the Duke of Burgundy, banned growing the Gamay grape in favour of Pinot Noir in order to improve the quality of the red wines produced in Burgundy.
Pinot Noir's main aromas as found in the red wines of Burgundy are nicely shown by a poster put out by the Bureau Interprofessionel des Vins de Bourgogne, which you can download here.