-Free experience can be used to research vehicles or modules.
-If you research a new module, free experience is used only after all regular experience has been depleted.
How to convert experience:
For one gold coin you can convert 25 experience points to free experience, but the experience you convert must come from an elite tank.
An elite tank is a tank that has had all the modules/tanks researched. When a tank gains elite status, a special sign appears on its icon so that you can easily see that it is elite.