WiFi and WLAN are essentially the same technology, with the difference lying in terminology and scope. WiFi (Wireless Fidelity) is a branded trademarked term used to certify that wireless devices meet specific IEEE 802.11 standards for interoperability and performance. WLAN (Wireless Local Area Network) is the broader technical category describing any local wireless network that allows devices to connect without cables.
Think of it this way: all WiFi networks are WLANs, but not all WLANs are necessarily WiFi-certified. A WLAN is the functional concept—a wireless network covering a limited geographic area like a home or office. WiFi is the commercial implementation and certification mark that ensures devices from different manufacturers will work together reliably using 802.11 standards.
In practice, the terms are used interchangeably in everyday conversation. When someone says their WiFi is down, they mean their wireless network isn't working. When a technical document refers to WLAN, it's describing the same wireless local network infrastructure. The distinction matters mainly in formal technical contexts, where WLAN is the standard term, and in marketing, where WiFi is the recognizable brand name that consumers understand.
Other wireless technologies can create WLANs—such as older standards like Bluetooth mesh networks—but these wouldn't carry the WiFi certification. However, this distinction has become increasingly rare as WiFi dominates wireless local networking.