Light is complicated as it can act as both a wave and as a particle.
A particle of light is known as a photon. These can be thought of as little packets of light, carrying energy. When we take a photograph on a modern camera, or on a telescope camera, we count these photons. The more we count the brighter an object is - we call this measurement the flux.
When light acts as a wave, it still carries energy, but it has a bunch of other information too. This helps us to understand more about it.
Every wave (e.g., light, water, or sound) has the following features: