A WiFi dongle, also known as a mobile broadband stick, is a USB device that allows you to access the internet.  These dongles are popular as they offer flexibility to the user. As they are not connected to a fixed-line, you can use them when traveling, or in various locations as they are easily transported.  

Simply connect the USB to a laptop, and it will enable internet access. The Dongles use mobile coverage so depending on the mobile signal your speeds may vary.