A Peripheral Component Interconnect (PCI, "Peripheral Component Interconnect") is a bus (picture 2) computer standard for connecting peripheral devices directly to your motherboard. Dimensions of the cards - PCI (standard) 107 mm x 312 mm (picture 1) - PCI Low Profile Height: 36.07 mm x 64.41 mm Depth: 119.91 mm to 167.64 mm - Mini PCI Mini PCI cards have a Maximum consumption2W.

The Wifi technology is a wireless communication mechanism between devices. This technology allows you to connect devices such as computers, laptops, mobile etc... to the Internet or communicate with the devices themselves.

Applications can be several, among the most common are the access points, ideal for giving and sharing a connection signal to multiple devices. It is the typical configuration of a home user.
Repeater, ideal to repeat and amplify weak signal.

The power and range between devices basically depends on the antenna and its hardware.

The wireless signals work under a unified standard regulations, the standard that is based on the IEEE 802.11. These include IEEE 802.11b, IEEE 802.11g and IEEE 802.11n working at 11 Mbit/s, 54 Mbit/s and 300 Mbit/s, respectively.
Being any device with a standardized protocol such technology can connect to another using the same technology, making it a kind of universal connection.

The wireless networks are characterized by the ease and convenience of making connections in infrastructure, since it is not necessary to perform network cable installations.
it also allows connecting a lot of devices to a single node.