Internet basics

Grandma:  Why are there always these abbreviations WLAN and Wi-Fi.  What is the difference?  What are WLAN and Wi-Fi. 
Anyway I'd best ask my grandson. 

Hello, this is Grandma Bess.  I have a question. What is the difference between WLAN and Wi-Fi?

Boy: Hello Grandma. WLAN and Wi-Fi are actually the same. 

Grandma: So, WLAN and Wi-Fi are pretty much the same. And what's a Wi-Fi good for? 

Boy: WLAN and Wi-Fi are networks without cables.  It needs a router that is connected to the Internet and devices, mobile phones or computers, that are logged into this network.  Then you can use these devices to connect to the Internet without wires.

Grandma: Let’s see, if I have understood you correctly.WLAN and Wi-Fi are networks without cables. 
It needs a router that is connected to the Internet and a device, a mobile phone or a computer, that is logged into this network. 
Then I can connect this device to the Internet without a cable.

Thank you very much. 
You have helped me a lot.

Boy: I love you Grandma.