If the price is at $5.60 and you want to buy if the price moves down to $5.40, then you would place a limit order at $5.40 - this means that you are prepared to buy at a maximum price of $5.40 or lower.
If instead you only want to buy if the price goes up to $5.80 or more, then you would place a stop buy market order at $5.80. This means that your order will hit the market when the price reaches $5.80 or above and be triggered at any price after that.
If you want your order to hit the market at $5.80 but only buy at a maximum of say $5.85, you would place a stop buy order at $5.80 with a limit at $5.85.
Why would you place an order to buy at above the current market price? Because you might be following some technical analysis trigger, example - a resistance line is just below $5.80 which has been hit on 3 occasions recently but not broken through. So you think to yourself that if the price breaks above this resistance it might move up strongly above it, so you only want to buy if the price hits $5.80 or above.