Why is Price Changing?

Why does this price keep changing? Why can't there be a fixed price?

This price that we see here is the price for the last trade that happened between a buyer and a seller. So, if we placed an order to buy 100 shares of DOD at rupees 41 and a seller placed an order to sell us 100 shares of DOD at rupees 41, the new price will be rupees 41.

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After this, if someone else placed a buy order for 25 shares of DOD at 40.5 and someone else agreed to sell 25 or more shares at that price, the new price will be rupees 40.5.

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Why does the price keep changing every second or so?

Because there are so many buy and sell orders happening all around the world. This makes it look like the price changes fast.