WPA-Enterprise, as the name says, is the authentication mode used in enterprise networks.
In WPA-Enterprise, the AP does not authenticate the client as in WPA-Personal mode, but instead delegates it to an Authentication Server (AS) that communicates with the AP through the RADIUS protocol.
The authentication packets exchanged between AP and AS are carried using the Extensible Authentication Protocol (EAP) and specifically the EAP Over LAN (EAPOL), a protocol defined in the 802.1x standard for authentication on wired LANs. The AP (authenticator) acts as a relay that forwards the authentication packets between the two parties, the client (supplicant) and the AS.
EAP is an authentication framework rather than a single protocol ...