First, the most basic statement that you need to understand is that news triggers price changes in the markets. Based on the information, users take decisions to buy or sell shares, which results in price changes of the events based on the demand and supply of shares.
Let's take an example event.
Event: Elon Musk to buy Twitter?
Initially, we all came across the news that Elon was interested in purchasing majority stakes in Twitter so the shares of YES were trading at approximately ₹ 70. However, once the deal was put on Hold, the shares for NO started trading at nearly ₹ 70 then. Thus, the value of the shares change according to the news and information out there.