Wi-Fi stands for Wireless Fidelity, and it is developed by an organization called IEEE (Institute of Electrical and Electronics Engineers) they set standards for the Wi-Fi system.

Each Wi-Fi network standard has two parameters :

1. Speed - 
   This is the data transfer rate of the network measured in Mbps (1 megabit per second).
2. Frequency - 
   On what radio frequency, the network is carried on. Two bands of frequency for the Wi-Fi are 2.4 GHz and 5 GHz. In short, it is the frequency of radio wave that carries data.

Two Frequencies of Wi-Fi signal :
Wi-Fi routers that come with 2.4 GHz or5 GHz are called the single-band routers but a lot of new routers support both 2.4 GHz and 5 GHz frequency they are called dual-band routers. 

The 2.4 GHz is a common Wi-Fi band, but it is also used by other appliances like Bluetooth devices, wireless phones, cameras, etc. Because of the signal used by so many devices, the signal becomes overcrowded and speed becomes slow. So 5 GHz comes into the picture, It is new, and not commonly used, and because it is used by fewer devices there is no signal crowding and interference.

The 2.4 GHz transmits data at a slower speed than 5 GHz but does have a longer range than 5 GHz. The 5 GHz transmits data at a faster rate, but it has a shorter range because it has a higher frequency.