In telecommunications, spread spectrum refers to when a signal, generated in one bandwidth, is spread across several frequencies to create a signal with a wider bandwidth. Doing this can result in more secure communications, a resistance to interference and jamming, as well as a lower chance of detection by another source. It can also benefit satellite downlinks by limiting power flux density.
The idea of spread spectrum was first thought up in 1900 by Nikola Tesla, then called frequency hopping. Commercial use of spread spectrum started in the 1980s. The FCC allowed for unlicensed use of spread spectrum starting in 1985 and over time, this paved the way for the introduction of Wi-Fi, Bluetooth, and cordless phones.