For example, EUR/USD is currently trading at 1.2050. You want to go long if the price reaches 1.2070. You can either sit in front of your monitor and wait for it to hit 1.2070 (at which point you would click a buy market order), or you can set a buy limit order at 1.2070 (then you could walk away from your computer to attend your ballroom dancing class). If the price goes up to 1.2070, your trading platform will automatically execute a buy order at that exact price.