wpa_supplicant is a WPA Supplicant for Linux, BSD and Windows with
support for WPA and WPA2 (IEEE 802.11i / RSN). It is suitable for both
desktop/laptop computers and embedded systems. Supplicant is the IEEE
802.1X/WPA component that is used in the client stations. It
implements key negotiation with a WPA Authenticator and it controls
the roaming and IEEE 802.11 authentication/association of the wlan
driver.

wpa_supplicant is designed to be a "daemon" program that runs in the
background and acts as the backend component controlling the wireless
connection. wpa_supplicant supports separate frontend programs and a
text-based frontend (wpa_cli) and a GUI (wpa_gui) are included with
wpa_supplicant.