wpa_supplicant is a client (supplicant) 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.