A proxy server acts as an intermediary between a user and a remote server by sending a request on behalf of the user, retrieving the response, and then delivering the data to the user. This approach eliminates the need for the user to send a request directly to the remote server every time, resulting in a significant improvement in access efficiency. Furthermore, the proxy server's caching function can reduce the number of requests sent to the outside world, thereby enhancing network security. Hence, proxy servers are an effective network tool.