Using an Ethernet shield along with Arduino board you can turn it
into a simple web server which can be accessed by anyone on the internet, and by accessing that server with a browser
running on any computer connected to the same network as the Arduino board,
you can:
- Control hardware from the webpage like fan or lights (using Javascript buttons).
- Read the state of a switch which can be either ON or OFF (using simple HTML).
- Read value of a sensors connected to Arduino board (using simple HTML).