What Is a Proxy?

A proxy, specifically a proxy server, performs intermediary tasks
between a requesting computer and another computer from which the
services are being accessed. It can be a dedicated computer or
software which catches the requests to the source server, caches the
data, and returns the information to the client computer. A proxy can
be used to improve web access performance, filter requests, or hide the
identity of the requesting party.

Data Caching to Improve Performance

The most common application for proxies is web caching. A web proxy
caches the information gathered from individual requests and stores
that data for a certain amount of time. When a computer requests a
web page or certain files that have been cached, the proxy server just
returns the requested data immediately instead of getting them again
from the source server, thereby significantly reducing access times.
If the data is not available on the cache, the proxy server fetches it
from the source server, saves a copy on its cache, and returns it to the
requesting client. Web proxies use algorithms to determine how long
cached data should be kept before purging them.

Web Filtering to Enhance Security or Improve User Experience

Another common use for a proxy server is web filtering and this
application is usually seen in corporate networks. A web filtering proxy
can prevent users from accessing sites and services that it deems as
not secure or inappropriate for the corporate environment. These can
be sites that contain malicious code and even viruses which can wreak
havoc on a computer and risk the security of the whole infrastructure
or a site with censored and offensive content. Other web filters can
reformat pages from the site for better viewing on mobile phones, or
for printing.

Anonymity

One popular proxy application for individual users is for hiding the IP
address of the requesting computer. There are sites offering what is
called CGI proxies in which they use PHP or CGI code to facilitate the
request, thereby providing anonymity to the client. The source
computer only sees the proxy server and not the requester.
These sites are often used by people who need access to sites that are
commonly blocked by web filtering proxies implemented in companies
or schools. And it’s because of that reason that most of these sites are
also blocked by web filters. There are sites offering anonymous proxy
services for free and some are paid.