Protocol: A set of rules and standards that govern the communication between two or more devices or systems. This is commonly used in networking and communication systems to ensure that different devices and systems can communicate with each other in a consistent and reliable manner. Examples include TCP/IP and HTTP.

Protocol converter: A device or software that converts data from one protocol to another, allowing different devices and systems to communicate. It is used in networking and communication systems to enable compatibility between different protocols, with examples including modems and gateways.

Protocol stack: A layered set of protocols that are used to implement a particular networking or communication system. This is commonly used in networking and communication systems to provide a complete and consistent set of protocols for a particular application. Examples include the OSI model and the TCP/IP stack.

Proximity Reader: A device that uses electromagnetic fields or radio waves to identify objects in close proximity. This is commonly used in security systems to authenticate users based on their proximity to a particular device or location. Examples include RFID readers and NFC readers.

Proxy (and Proxy Server): A system that acts as an intermediary between a client and a server, often used to mask the client's identity, implement access policies, cache content, and improve performance. Proxies can function at various levels of the network protocol stack and are widely used to enhance security, privacy, and control over internet traffic.

Public cloud: A type of cloud computing service that is provided over the Internet and is available to the general public. This is commonly used by organizations and individuals to access and use computing resources on demand without the need to purchase and maintain their own hardware and software. Examples include Amazon Web Services and Microsoft Azure.