What does a/b/g/n means in WiFi , IEEE 802.11 Standards

WiFi , that stands for Wireless fidelity is a popular technology used  that allows electronic devices like Laptops , Tablets and Smartphones to transfer data over wireless networks. It is also similar to WLAN or wireless Local area network and technically WiFi is  another name for IEEE 802.11 standard. The technology was released back in 1997 and was the term WiFi became popular in 2000s.The IEEE 802.11 is nothing but Wireless Fidelity or commonly known as WiFi. Like any software has many versions , similarly WiFi has several versions  that are a , b , g and n respectively The a and b version standard are older while g and n belongs to the latest member of standards. 

1. IEEE 802.11a
The older version 802.11 a was the first version of WiFi or IEEE 802.11a and it operated over 5 GHz frequency and was capable of supporting Bandwidth of maximum 10-15 Mbps speed while the theoretical claim was 54 Mbps. The limitation of less range existed and and was too slow to be use in current days and 802.11a products are no longer manufactured.

Pros of 802.11a: Signal Strength with in range was Good
Cons of 802.11a:  More expensive and less range

Fact: 802.11a and 802.11 b versions were built at the same time but however 802.11a was more expansive than b version and its use was limited  in Business N/w's while b version became popular for home purpose.
2. IEEE 802.11b
The Second Versions 802.11 b  started in 1999 operated at frequency of  2.4 GHz and claims to provide theoretical speed of  11 Mbps with in 30 meters ranges while the practical speed  was much lesser.

Pros of 802.11 : Less Cost/ In expansive
Cons of 802.11:  Slower maximum speed , Interference from home appliances 

3. IEEE 802.11g
802.11g version is advanced compared to above two versions and emerged in 2003 and it combines the best elements of both a and b versions. With maximum bandwidth of network is 54 Mbps and operated over 2.4 Ghz for maximum range. The WiFi g standard is completely compatible with b version that means same access point can be used for both b and g versions. It has range of about 100-150 feets.
Pros of 802.11g: More range , More Bandwidth
Cons of 802.11g: Costs more , Interference from nearby appliances exist.

4. IEEE 802.11n
The latest 802.11 n version is the latest member  of  WiFi and improvement in bandwidth is achieved as it employs MIMO technology that means using multiple Wireless antennas. Data rates of above 100 Mbps is there in n version as well as has better range than above because of increased signal intensity.
Pros: Increased Range with Bandwidth
Cons: More Cost as well interference on account of multiple signals exists.