This post describes the sequence of events when before a URL is loaded in the web browser.

1. When you type in www.google.com, the brower asks the OS to find the IP address of the remote webserver which has the name www.google.com. If the OS does not know it already, it asks DNS server.
2. Once the IP address is obtained from DNS server, a TCP/IP socket connection is established on port 80.
3. Once the connection is established, a HTTP GET request is sent to through the connection to the remote webserver.
4. The webserver will give back a http a HTTP response which typically includes a HTML page. Additional resources within the page like stylesheets, images, etc are requested by browser in the background.