Light is weird. Light or Electromagnetic Waves are well, waves. They are a result of a changing oscillating electric field and a magnetic field. Sometimes we call them Photons, massless high-speed subatomic particles, coming in packets called Quanta. Wave-particle duality is only the brief introduction of the enormous and extraordinary area within Physics called Quantum Theory.
A slinky is a nice little demonstration of how light travels. Light is a transverse wave so it vibrates perpendicular to the direction of energy travel. In Third Year of High School, my Physics teacher used a slinky as an example to illustrate this feature of a transverse wave and also the other, longitudinal wave, which is a wave in which its vibrations are parallel to the direction of travel. Two people held the slinky at the two ends and one begins to vibrate the slinky coils left to right.
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