A proxy is a server that is capable of hiding your IP address from the public. There are various different forms of available proxies – major types including proxy servers (you are able to configure settings for these within your browser) and web-based proxies (which do not require that you modify any of your current computer settings).
It is very unfortunate to report misuse of such wonderful tools. They are often used illegally at work/school (in order to get around content filters to visit unpermitted websites, including social networking websites). Server administrator’s do their best to block proxies on content filters for this very reason.
Proxies can however be used for legal actions – and prove to be very helpful. One of such uses is to use a proxy to browse newly constructed websites (in the case that your ISP has not updated DNS settings, or you have a cached version of the website already stored on your computer). They can even be used legitimately in cases that content filters have made mistakes and have spotted one or two words that it deems inappropriate.
There are a lot of proxies available for use on the Internet, as a lot of money is up for grabs in the niche. If you are stuck, and unable to find any, refer to what are called “proxy topsites” (a great one is @Proxy). Proxy topsites offer lists of web-based proxies. Most categorize proxies by software type (the most commonly used are PHProxy and CGIProxy).