Pairs with 短仓 (short position). 长仓 = bet that prices will rise; 短仓 = bet on a fall. The mainland often uses 多头 ('long') and 空头 ('short') instead; 长仓/短仓 are more common in Hong Kong and Taiwan financial press.
memory
仓 originally means 'storehouse'; in finance it became the standard word for a 'position' (your inventory of assets). 长 = 'long'-term bet on the direction; 短 = 'short'.