Platform

A software environment that is used to write applications and run them. It includes software tools such as GUI builders, compilers, class libraries, and utilities for developing the applications, as well as a runtime engine for executing the applications, because they are not able to run on their own. Sun's Java and Microsoft's .NET Framework are examples of major software platforms. -PC Magazine Encyclopedia

PLC

Programmable Logic Controller (PLC) is a programmable microprocessor-based device that is used in manufacturing to control assembly lines and machinery on the shop floor as well as many other types of mechanical, electrical, and electronic equipment in a plant. A PLC is designed for real-time use in rugged, industrial environments. Connected to sensors and actuators, PLCs are categorized by the number and type of I/O ports they provide and by their I/O scan rate.

Protocol

A set of rules governing the exchange or transmission of data between devices. -Google

Polling

1- Refers to actively sampling the status of an external device by a client program as a synchronous activity. -Wikipedia

2- Polling rate in Ignition refers to how often Ignition will query the database for updates and how often it will update the data in the runtime Clients.