There are two basic types of resources in Hackers: $ (money) and B-coins. Both resources are used for building and upgrading nodes. B-coins are also needed for compiling and upgrading programs. Both B-coin and money can be generated by Business Nodes: Server Farm nodes produce money, and B-coin Mine nodes generate B-coins. The Database and B-coin Mixer nodes are used for storing additional $ and B-coins. When a player attacks your network, they can steal a maximum of 30% of your total resources. 
Credits are a special resource type which can not be stolen. Credits can be used to instantly compile programs and complete node upgrades, or to buy more Building Threads. They can also be used to purchase various content on the Black Market, including Shields to protect your network from attacks for a certain amount of time, Skins, or to fill up your resource stores. You can gain Credits by finding credit cards or watching ad videos on the World Map, or through in-game purchases.