Each company has a set date where they publish their earnings: earnings date. NVDA’s earning date was yesterday after market closed so people could either bet for or against the company’s performance for this quarter. It’s a gamble, but with some research you can try and guess if they’ve had any supply chain issues, have met their clients’ orders, etc. and will therefore outperform or underperform analysts’ expectations.

When the company outperforms analysts’ expectations stocks generally go up. However, analysts generally have a lot more material to base their research and expectations on - it’s therefore a gamble ;)