In wave analysis, finding the impulse and its correction is a primary task to predict the price flow. Most of the time this action, decides the price movement in market.
Improper prediction may lead you into a failure or loss.
IMPULSE: Candles use to appear with strong potential towards a particular direction. (Either Bullish/Bearish). and the trend continue into the same direction.
CORRECTION: Max. it follows with a Impulse, the corrective candles show up with less momentum. And moves in a particular direction of the market. the price may change its direction.
I hope, this will give you a clear difference between the Impulse and correction. These are my understanding about Impulse and correction. You may differ from that. Eg.