Sort:  

Put options, shorting a stock, or short
selling is betting that a stock will tank.
It's a risky endeavor but their are gains
to be made with that particular tactic.
https://www.investopedia.com/terms/s/shortselling.asp

Same thing in the crypto market, when Bitcoin up to a high, like 10K USD, or maybe 20K, then many people sold their Bitcoin, perhaps, right? But then again, if you sell your Bitcoin, then somebody else will have that Bitcoin, right? So, why would the value decline in Bitcoin?

Coin Marketplace

STEEM 0.26
TRX 0.20
JST 0.038
BTC 95614.30
ETH 3599.83
USDT 1.00
SBD 3.79