What is meant by an HTTP proxy server, and why are they used?

Answer, variant 1

An HTTP proxy is an intermediate agent between the HTTP client and the HTTP server storing a page to be downloaded. Such intermediate agents can cache copies of recently accessed pages, so that users get them faster and at less load on distant network connections. They can also have functions to stop viruses and other unsuitable content. They share the problem which most caching schemes have, such as that there may be a risk that users get outdated versions of a recently changed web page.

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