PND or pump and dump groups are consist of a group of traders which has some cooperation in their trades,they will pick some coins which they will pump with some target sell points which if they are done taking profits they will dump the coin,most of the newbies are getting victim of these PND coiins,exchanges doesnt allow these PND groups so you shouldnt be joining any of these because if you get caught ther are consequences for you lastly it wont improve your trading skills because you are relying to these ariticial PND groups.
So that might be a major reason behind instant market highs and lows at most of the time.