From Official Wiki of the Renaissance Kingdoms

Beer, and the church mass, are essential factors in increasing the mood of your character.

It is possible to drink beer in the taverns in the village.
And when opening a barrer of beer you get 100 pints of beer in your inventory, that you can either drink or move to your tavern

A barrel of Beer

It is produced in an abbey , thanks to their Brewing workshop.

A Barrel of Beer is sold for 60 to 100,95 pounds.

It has a weights of 8

However, the abbeys aren't everywhere and can be a long time to travel to, so the tavern owner can buy pints of beer without having to restock barrels from the abbeys (although this is much more rewarding).
The price for those pints are 0.80 pounds and are directly placed into the inventory of his tavern.

And with each event you can sometimes win one barrel.

A pint of beer

Using a barrel of beer from your inventory gets you 100 pints of beer in your inventory.

A pint of beer is sold for 0,05 to 5,95 pounds in the tavern. Or sold on the market for 0,00 to 1.95 pounds.
Note : it is impossible to buy something for 0,00 pound.

It has a weights of 2.

The tavern owner can put those pints straight into his taverne to restock it.

Side note: With a quick calculation, you can surely understand that it is not profitable to buy a barrel of beer for more then 80 pounds .