Long / Short
Long = profit on rise. Short = profit on fall.
Long: classic buy, sell higher. Short: borrow asset, sell, wait for drop, rebuy cheaper, return, keep difference. Long max loss 100% (price to 0). Short max loss infinite (price can go to infinity).
In plain words
Long = bet price goes up (regular buy). Short = bet price falls (exchange lends you the asset, you sell high, later buy back low and return it). Long max loss = 100%, short = theoretically unlimited. That's why beginners shouldn't short.
Example
Long BTC 50k→70k: +40%. Short BTC 70k→50k: +28% (sold 70k, rebuy 50k, $20k profit). Short BTC 70k→100k: -43% (sold 70k, must rebuy 100k = -$30k loss).
Also known as: long, short, long short