@asu you must be knowing what is a default gateway if you don't know let me tell you it is simply a router and when you try to connect to your internet you need the address of your default gateway and you can find it out easily because it is always in your computer.
what is the use of it
A default gateway is the device that passes traffic from the local subnet to devices on other subnets. The default gateway often connects a local network to the Internet.
Reference for this information is here