The price difference is that the market consists of buyers and sellers. If the buyer's asking price equals or exceeds the seller's asking price, the deal is made. Then there must be a distance between the purchase price and the selling price of the unfinished orders in the market. This minimum distance is called the price difference. If you take stocks as an example, then the spread is the difference between selling a price and buying a price. The same is true of foreign exchange. So the spread should be generated automatically by the market, not fixed. However, due to the different nature of traders in the foreign exchange market and the different ways of collecting commissions, a special form of fixed interest spread has emerged.