Just think of it as the price each trader is willing to buy or sell the coins on the exchange because that's exactly what it's. Buyer A might want to buy at a certain price but will later change his mind the movement he see a downward trend of the price same in the case of the seller, when the market begin to show positive signs of upward movement, the sellers immediate cancel his order so as to sell higher than the initial amount.

This are done by active traders but mostly bots which is why if you didn't keep your emotional understand control while trading, you can easily get decieved by the movement you're f the market.