EMZETT.Wireless
In short: Umbrella term for any form of wireless (radio-based) data transmission — includes Wi-Fi, Bluetooth, mobile networks and NFC, among others.
In more detail: Unlike wired technologies such as Ethernet, wireless uses electromagnetic waves for transmission. The advantage is flexibility (no cabling needed); the drawbacks are usually shorter range, greater susceptibility to interference and, on average, lower speed compared with cable connections.
In Depth
The various wireless technologies differ greatly in range, speed and energy consumption, because each was optimised for different purposes: Wi-Fi offers high bandwidth over medium distances (typically 10–50 m, ideal for a home/office), Bluetooth bridges short distances with very low power consumption (ideal for headphones, wearables), mobile networks (4G/5G) cover large areas, often for kilometres, and NFC works over a few centimetres for maximum security in contactless applications.
A fundamental physical principle that applies to all radio technologies: higher frequencies tend to allow more bandwidth, but have a shorter range and are attenuated more easily by obstacles (walls, furniture) — this is exactly why the 5 GHz Wi-Fi band, for example, offers more speed than the 2.4 GHz band, but a smaller effective range indoors. Susceptibility to interference arises because several radio technologies have to share the same free frequency range (e.g. Wi-Fi, Bluetooth and microwave ovens all use the 2.4 GHz band) and can therefore interfere with each other.