System identification is like when a detective solves a mystery. The detective has to look for clues and figure out what happened in the past, based on the clues. In system identification, "clues" are like measurements that are taken of a system. A system could be something like a car engine, and the clues could be measurements of how the engine is running. The system identification process takes all the measurements and uses math to figure out how the system works and what the best settings are for it.