A proxy is an intermediary server or service that acts as a gateway between a user's device and the internet. When a user sends a request, such as accessing a website, the proxy forwards this request to the destination server on their behalf. The response is then relayed back through the proxy to the user. Proxies are commonly used to enhance privacy, improve security, control internet usage, and bypass geographic restrictions. They can be implemented in various forms, including web proxies, reverse proxies, and transparent proxies, each serving different purposes within network architecture.