Yes, they are different although most people regard them as being one and the same.
They are not. WLAN is an acronym for Wireless Local Area Network while Wi-Fi is described by the Wi-Fi Alliance as being any WLAN that is based upon IEEE 802.11 standards. To be Wi-Fi certified, the WLAN must successfully complete Wi-Fi Alliance interoperability certification testing.
So, while any LAN that is Wi-Fi certified is regarded as a WLAN, UltraXtend wifi Erfahrungsberichte not all WLAN are Wi-Fi certified.