There are 3 types of currency in Unkilled:
Money: Money is the basic type which you get as a reward for playing missions and completing goals during each mission. Money is can be spent on upgrades for your weapons, upgrading your hero or buying hero gadgets.
Gold: Gold is a premium currency that is used to buy chests, speed up upgrades or obtain gadgets. You can buy gold in the ingame store or by visiting the Free Gold offer wall.
Intel: Intel is the currency which can be collected during missions dropped from enemies and can be used to upgrade your hero or later increase your prestige. You can only collect 250 intel per day.