Radio spectrum is the invisible medium that carries all wireless communication. Think of it as a highway where different wireless technologies occupy different lanes. Frequency, measured in hertz, describes how rapidly a radio wave oscillates per second. Mobile networks operate in the megahertz and gigahertz ranges, with each operator licensed to use specific slices of spectrum. The choice of frequency involves a fundamental tradeoff that shapes every wireless network design decision: lower frequencies travel farther but carry less data, while higher frequencies deliver blazing speeds but cover much shorter distances.