A spot trade is the purchase or sale of a foreign currency, financial instrument or commodity for instant delivery. Investopedia
On Liquid, spot trading is available under EXCHANGE. This is your normal buying/selling. You spend one currency to get another without getting a loan.
One "spot trade" is completed with one single order.
Margin trading refers to the practice of using borrowed funds from a broker to trade a financial asset, which forms the collateral for the loan from the broker. - Investopedia
A margin trade is basically a bet, made with borrowed money, on 1/ which way a product price will move and 2/ how much it will move.
One margin trade involves two orders.