Here I am looking a bit to buy a laptop online, and I often come across descriptions that say: "wireless LAN", but what does that mean???? Does this mean that the laptop has built-in Wi-Fi or the opposite???
No, just wait until you have the icon (a screen) and a message in your toolbar (at the bottom) indicating that you have the option to connect. At that point, you go to the list of available networks and choose according to whether you are with Free, Neuf, etc. Then, you connect via the internet and "it" will ask you for your username and password.
You can also get a Wi-Fi key, it's another option, one doesn’t exclude the other.