The spectrum both surrounds us and passes through us. Made up of waves of energy that allow us to communicate the way we do today – through radio, television, mobile phones, wireless internet and more — spectrum is an invisible common link that ties our societies together. A global shift in spectrum regulation is currently under way with regulatory reforms being developed and proposed in several countries. As the internet and wireless communication increasingly merge into a singular form of communication, we will be presented with unique opportunities to adapt to open, trusting and collaborative forms of regulation and technology use. This introduction to developing a policy on open spectrum by spectrum expert Evan Light for APC, breaks down what spectrum is, how it works and why governments with under-served communities stand to gain so much from opening up the spectrum to more users and uses.