PdM goes a step past condition-based maintenance: instead of reacting to a sensor crossing a fixed threshold today, it looks at the trend — vibration climbing steadily over three weeks — and projects forward to estimate when that trend will reach failure, so the work order gets raised while there's still lead time to schedule it properly.
It needs a history of data to work from, which is why PdM programmes usually mature out of a condition-monitoring rollout rather than starting from nothing — you need weeks or months of baseline readings before a trend means anything statistically.