In World of Tanks, there are four types of in-game resources and currency.
Experience is an in-game resource earned in battles. There is Combat Experience, Free Experience, and Crew Experience. Combat Experience includes experience earned on researcheable and Elite vehicles. Combat Experience is earned on each vehicle separately. Combat Experience earned on a researchable vehicle is used to research its modules and subsequent vehicles. Premium vehicles and vehicles with all modules and subsequent vehicles researched have Elite status. Combat Experience earned on Elite vehicles can either be used to accelerate crew training or be converted to Free experience . Crew experience is used for crew training.
Credits are the main in-game currency. Credits are used to purchase researchable vehicles, modules, consumables, and equipment, as well as to repair your vehicles and train your crews.
Gold is an in-game currency that can accelerate your in-game progress. Gold is used to purchase Premium vehicles and Premium Account, convert Combat Experience to Free Experience, and do many other things.
Bonds are a special in-game currency that is earned in special battle modes and certain in-game activities. Bonds are used to purchase vehicles, improved equipment, and directives for equipment in the in-game store via the (Items for Bonds) section.
You can view your resources and currency in the top right corner of your screen.