The barrel, or rather the cask, makes you want to shout "cock-a-doodle-doo" because it was the Celts, and more precisely the Gauls, who invented it. It allows the maturing of the wine.
It was first and foremost for the convenience of transport that the barrel was invented, with the flourishing trade around the Mediterranean in antiquity. At the time, we didn't yet speak of wine, but of cervoise, which Asterix fans at least know the name. With the Roman conquest by Julius Caesar, itself described in Goscinny's comic strip, the barrel will become popular throughout the Roman Empire.
However, the maturing of wine in barrels is necessarily accompanied by a loss of part of the wine, insofar as this is absorbed by the wood. This stage, known as "prise de bois", makes the wine very dry because the tannins in the wood have penetrated it. But it is only in the first few months that this phenomenon is observed and with time, there is an attenuation and then a rounding of the wine which is ready for tasting, generally 12 to 18 months later.
Above all, the barrel will give new aromas to the wine. Take the oak barrel for example, notes of coconut, vanilla or fresh wood will develop. There is also a more or less strong bitterness when taken in the mouth.
The size of the barrel is extremely important as the volume of wine and the contact surface will determine the aromas that will permeate the beverage or not.
The origin of the wood is also important. Globally, French oaks, especially those from the Allier (Tronçais forest) are known for their finesse, whereas the American oaks, which are less fine, give off more aromas.
Moreover, the age of the wood used to make the barrel is of great importance in the ageing of the wine. A new barrel will be more suitable, as it has not yet taken in other wines, and therefore is not likely to provide the aromas of another wine. This would provide unsuitable aromas.
But the most important factor will be the quality of the wine used. It is indeed said that the wine must be able to withstand the barrel and a wine that is too light will not be enhanced by this practice. This is why barrel ageing is very often reserved for ageing wines.