Equity prices change every day based on supply and demand. If more investors want to buy a share than sell it at the current price, the price goes up. If more want to sell than buy, the price goes down. In the process, the market incorporates the views of everyone who transacts. The result is that prices are hard to forecast. Some people find this counterintuitive. In most endeavours, if you are smarter and work harder, you can do better than others in your field. Investing in public markets is different though. Intense competition makes it unlikely that an investor will regularly know more than everyone else or profit from exclusive information.
Fortunately, you can win without playing the game, as fair pricing lets you benefit from what equity capital markets offer.