En Primeur is a French wine trade term for wine which is sold as a 'future' i.e. buying of wines at its initial offering price when they are still in barrels, before it is ready to be bottled and delivered.
After the harvesting around September-October and carrying out the usual fermentation, Châteaus will invite members of the international wine trade to taste and assess these wines around March in the year following the harvest. Châteaus will release a strict allocation of their total production at a pegged price to négociants (wine brokers), who then releases these wine to wine merchants around the world.
The wine merchants will then offer the wines to its customers with the promise that wines will be delivered at a later date but at a fixed price now. Customers will also need to pay other charges including shipping cost, freight insurance and duty charge.
WS = Wine Spectator, WA =Wine Advocate, JS = James Suckling, AG = Antonio Galloni