WiFi stands for Wireless Fidelity which is nothing but Wireless Networking. WiFi in a PC or Laptop means that the Device is equipped with a WiFi Adapter and can be connected to a Wireless Network without any additional Hardware Requirement. WiFi Environment means that Wireless Network is available and PC or Laptop with Wifi ready can Connect to the Network Wirelessly.

If You Want to Make a PC WiFi Ready, Just Add one wifi adapter to it, which could be an internal card which fixes inside a pc or a USB dongle connected on a USB port externally.