In order to aid progression for players who have reached tier V and above, Wargaming is introducing a new system to their title, called the "Blueprint" system. These Blueprints will drop in a percentage of matches played in vehicles of tier V and above, and cannot be purchased with any of the currencies available in the game. Blueprints will reduce the cost of researching a corresponding vehicle from tiers II to X, but not its associated modules, and are more likely to be dropped if you play more effectively. You can receive multiple blueprints for a vehicle, incrementally reducing its research cost to a maximum of 100%. Should you earn a blueprint for an already researched vehicle, it will be converted into either a "Universal" or "National" Blueprint. Universal Blueprints can be applied to any vehicle, and National to any vehicle of the same Nation as the original already researched vehicle. 4 Universal Blueprints and one National Blueprint can be combined to create a Blueprint for a specific vehicle.
Please note that this feature is a work in progress, and details may change in future. More information can be found at the following link:
(Below is an example of a complete Blueprint for the P26/40 Medium Tank, created utilizing the interactive tool at the linked page)