Light is about seeing things.
When I see you, it's because there is light.
I cannot see light itself, but thanks to the light you emit, I can see you.
If we discuss light in physics terms, we have known since Maxwell's time that light is a wave, an electromagnetic wave. In other words, light represents variations in a magnetic field.
To this, quantum physics has added the notion of a photon: light is also particles, tiny particles that leave a source and move towards you.
The question of how light can be both a wave and particles at the same time is answered by quantum physics, but I won't give you the answer right now because we would be here for a very long time!
What we usually tell people (and I quite like this way of putting it) is that light behaves as particles when you're looking at it, and as a wave when you're not!