If you want to hide your location (your IP address) from prying websites or applications, you can use a proxy server. A proxy server is a computer set up to accept your requests (such as "show me http://yahoo.com"). The proxy server executes the request, receives the requested data and sends the results to you. This way, Google thinks the request came from the proxy server, not from you. Your location is hidden from Google.
You can use a proxy server when you post data to a website, also. One reason marketers may want to use a proxy server is to remove the customization that Google "helpfully" includes in your searc h results. It knows something of your surfing history and knows some of your preferred sites, some of your likes and dislikes. It tailors your search results to reflect what it knows about you. Usually this is helpful, but sometimes (for example, when you want to know a site's ranking in search results) you want unbiassed data, not influenced by who you are. A proxy server provides this.
