@Guildford Do you mean "dark matter"? No. We do not yet know what dark matter is exactly, but we can constrain its properties pretty well - it's matter :)

For the concept of energy, here is a rather good intro: https://www.khanacademy.org/science/hs-physics/x215e29cb31244fa1:introduction-to-energy/x215e29cb31244fa1:forms-of-energy/v/introduction-to-energy