EDAC
Beginner
Extra check bits stored with data, so the chip can spot and fix mistakes.
Novice
Error detection and correction: extra check bits stored alongside each word of memory, computed so the chip can tell when a bit has flipped and put it right.
Expert
Common codes are Hamming SECDED (single-error correct, double-error detect) and Reed-Solomon, which corrects bursts. Pair it with scrubbing so a single error is fixed before a second hit in the same word makes it uncorrectable.