Wifi Basic

There are several kinds of hardware that may be used to implement a WiFi wireless network:

• Wireless adapters or network interface controllers (NICs for short) are network cards with the 802.11 standard which let a machine connect to a wireless network. WiFi adapters are available in numerous formats, such as PCI cards, PCMCIA cards, USB adapters, and CompactFlash cards. A station is any device that has such a card.
• Access points (AP for short; sometimes called hotspots) can let nearby wifi-equipped stations access a wired network to which the access point is directly connected.

The 802.11 standard defines two operating modes:

• Infrastructure mode, in which wireless clients are connected to an access point. This is generally the default mode for 802.11b cards.
• Ad hoc mode, in which clients are connected to one another without any access point. 

Further information fallow  this link:   http://en.kioskea.net/contents/wifi/wifimodes.php3