Gold, elixir and dark essence are the basics of the game, they are called the coc main currency, there are also gems, but thats different subject.
Most primary are gold and elixir - you will use it to build up your buildings, upgrade defenses, construct troops and after spend whole lot of for upgrading the walls.
Gold can be gained from the ground through gold mines and after that is stored in your chests which you have to protect from other players. You will need a lot of gold to upgrade your hall. Keep in mind you need a storage to store all that gold so if you run out of room you need either build new storage or upgrade existing one, thats really important because many players forgets about it and just keeps losing gold.
The purple elixir is gained from buildings called collectors and after that is stored in essence storage. It is primary resource to produce troops and upgrade buildings and more importantly wall's later!
Dark essence is gained from drills, you don't get that building early in the game only later and you will need a lot of it to build your first clash of clans heroes, it is also primary resource to upgrade advanced units and to produce dark elixir units which are more advanced and have a lot more firepower than standard ones. They can be used to launch successful attack on your enemy because they consists of special abilities.