Here are the Antenna of wireless router and the antenna of walkie talkies. And the tenda devices that i used to spread wifi signals at my home.
These antennas are used to capture the weak signals that can not be captured using the device without antenna. Some devices have one antenna some have 3,4,5 its depend on how powerful a device is and how costly it is. These are all help to serve the internet. Thanks
@jonybraim