Buy / Sell

Buy (going long) means purchasing an asset expecting it to go up. Sell (going short) means selling it expecting it to go down — usually by borrowing the asset first and buying it back later cheaper. Being able to profit in both directions is what makes markets symmetric; without shorting, prices only correct downward when holders voluntarily sell. Retail brokers handle long positions natively, but shorting requires a margin account and carries tail risk — the price has a ceiling of ∞ working against you. Day trading, swing trading, and position trading are just different timescales on top of these two basic actions.