Ad-Hoc mode is a method for wireless devices to directly communicate with each other. It allows wireless devices within range of each other to discover and communicate in peer-to-peer fashion without involving a central access point or wireless router.
To set up an ad-hoc wireless network, each wireless device must be configured for ad-hoc mode versus the alternative infrastructure mode. In addition, all wireless devices on the ad-hoc network must use the same SSID and the same channel number. Ad-hoc networks cannot bridge to wired LANs or to the Internet without installing a special-purpose gateway.
Ad Hoc mode LANs are normally less expensive because they do not require a dedicated computer to store applications and data. However, they do not perform well for large networks.