SCADA stands for Supervisory Control and Data Acquisition.

In most manufacturing processes, you have devices, usually called PLC or Programable Logic Controllers. These will be simple controllers to measure values, or turn relays on or off, start or stop motors etc.

SCADA gives the human operator a GUI across one or more PLCs. It's just computer software, often written in C or similar languages, that sits above and controls the PLCs.

Iranian centrifuges were damaged when hacked SCADA was showing operators one thing, eg safe rotational speed, while doing something else entirely, eg winding them up to damaging speeds.