Wifi is the technology that provides the way to connect the network of the other devices or internet wirelessly. Basically Wi-fi term defines the Wireless local area network, short form is WLAN that based on the IEEE 802.11 standards(Institute of Electrical and Electronics Engineers). Today Wifi is the popular technology to exchange the data over the network, most of devices has the inbuilt wifi technology.
Smartphones, personal tablets and computers, video games,music devices and several other devices uses the wifi to connect the Internet through a wireless network access point, this is the very convenient way of the internet connectivity.
For the Internet access
The figure1 shows the how the internet access is distrubuted among the wi-fi enabled devices through the router device (with access point). Wireless access points can be integral part of the router device. A router sends information between your network and the Internet. With a wireless router, you can connect computers to your network using radio signals instead of wires. So you can connect muliple devices from the internet with the single access point.
There are a few different types of wireless network technologies, including 802.11a, 802.11b, 802.11g and 802.11n. if you using the router device, it is recommended to use a router that supports 802.11g because it is fast and provides a strong wireless signal.
Currently, there are four WLAN standeards: 802.11b, 802.11a, 802.11g, and 802.11n. The following are the short description of each.
802.11b
802.11b has a maximum raw data exchange rate up to 11 Mbps(megabits per second). The overall signal strength is good but has slowest data exchange rate in compare of other standards. It uses the 2.4 GHz frequency which can cause interference.
802.11a
802.11a has a maximum raw data exchange rate up to 54 Mbps(megabits per second) that is faster than 802.11b. It uses 5 GHz frequency which limits interference from other devices. It is not compatible with 802.11b network adapters, routers, and access points.
802.11g
802.11g has a maximum raw data exchange rate up to 54 Mbps(megabits per second) and has good signal range and isn’t easily obstructed. It uses 2.4 GHz frequency which which can cause interference(same as 802.11b). It is compatible with 802.11b network adapters, routers, and access points.
802.11n
802.11n can transmit data at up to 150 Mbps, 300 Mbps, 450 Mbps, or 600 Mbps depends on the hardware support. It has the fasted exchange rate. It can use both(2.4 GHz or 5.0 GHz) frequencies. If this will use 2.4 Ghz frequency If using the 2.4 GHz frequency, it can have the same interference problems as 802.11b and will compatible with 802.11g network adapters, routers, and access points.
device-to-device communication
Wi-Fi also allows communications directly from one device or computer to another without an access point intermediary. Simply this type of network is called by ad hoc Wi-Fi connection. In an ad hoc network, computers and devices are connected directly to each other, rather than to a hub or router or any access point.
Wi-fi technology allow to easy implementation of the LAN(Local Area network). There are many cities that have the entire city Wi-fi implementation, Sunnyvale, California(USA) and London (UK) are one of them.
Other Sources:
Wikipedia