Difference Between PLC and SCADA?

PLC

A Programmable Logic Controller also known as PLC, is a piece of hardware used to read sensors.
PLCs receive information from connected sensors or input devices, process the data, and triggers outputs based on pre-programmed parameters
They were initially developed in the automobile manufacturing industry to provide heavy duty, programmable controllers to replace hard-wired relays, timers and sequencers.
They are now used as automation controllers suitable for harsh environments in many different industry processes.
PLCs are also used to function as real-time systems, since output results must be produced in response to input conditions within a limited time, for continuous proper operations.

Supervisory Control and Data Acquisition (SCADA) is monitoring software used to control the PLC and record data, even from remote locations.
SCADA systems use computers, networked data communications and graphical user interfaces for high-level process supervisory management by relying on PLC’s and discrete PID controllers to interface with the process plant or machinery.
SCADA systems are managed by an operator using an operator interface which allows the individual to monitor and the issue process commands through the SCADA computer system.