What is WLAN?
WLAN or a Wireless LAN is a network that assists communication between two computers without having to be wired to each other. This is useful because you can move your device to different place without loss of Network and it helps reduce cluttering of wires.
What is Wi-Fi?
Wi-Fi is just a wireless standard 802.11. There are differenet versions for 802.11 which are written in compatible with the 802.3 Ethernet which are the bridged together using Access Points (APs)

Wi-Fi vs WLAN
Wi-FI networks are essentially WLANs. But Wi-Fi is not the only WLAN available. It is the only WLAN that is used bt the human clients directly while most other WLANs likely service headless client device nodes.
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