Open two terminal emulators and start netcat in both, using the nc -l 1234 command in the first one and the nc 127.0.0.1 1234 command in the second one. The order is important! nc is the name of the netcat program, -l 1234 instructs it to listen for connection at port 1234. After this every line you type in one of the terminals shows up in the second one.

The single line command:
echo -e 'GET\n' | nc www.yahoo.com 80
dumps the first page of yahoo on your screen.

To see how your browser is requesting the webpage type in the command
nc -l 1234
Then type in http://127.0.0.1:1234 into your browser's address line.