Just like what it happens in a real life situation, when you are doing a pump you are putting a pressure that results into the rise of a certain object. That is also what really happen in the market industry. Price values of various types of cryptocurrency undergoes a certain process of pumping and dumping which normally happens with the sudden exchanges of price value in the market. Also in cryptotrading. The rise of the btc value for buying a certain altcoin is an indication that it is now time to sell some assets you are holding for trading.