When you place an order according to market, your order will be executed according to the current market price. 

When setting a limit for buying orders, your order will be executed according to your limit price or lower. 

When setting a limit on a selling order your order will be executed according to your limit price or at a higher price than your limit. 

Finally, a stop loss is an order type which allows the investor to trigger a sale order at a certain price level. E.g. if the current market price is €100, and a stop loss order is placed at €95; once the market price falls to €95 or below a sale order at market (next available price) is triggered.