Answer:
PLC stands for Programmable Logic Controller. Basically its like a small computer that uses simple logic to execute automated processes, like in a factory. Lets say there is a factory that test balls for color. The desired color is Red and any other color is discarded. With the help of senors, the PLC will determine if the Ball is of Acceptable color and either trigger a sequence that transfers the ball to a different location, or kicks the balls of different colors out from the Passable balls. There are many types of PLC's. Some examples are SLICK 500 and Allen-Bradley. How ever this is only a small example of what PLC's are capable of doing.