Nvidia sells graphics processing units (GPUs) that provide computing power for various uses. More than two decades ago, the main function was to support PC gaming. But what has put the business on the map in recent years has been its GPUs that enable training AI models in massive data centers, now representing the bulk of the chipmaker's sales.

Chipmaker and AI darling Nvidia is back nipping at Apple's heels as the most valuable company in the world, with the stock hitting an all-time high Monday.

NVIDIA (NASDAQ: NVDA) is still the most important stock after two-plus years of dominating the stock market. Its GPU technology unlocked the door to AI, and now NVIDIA is capitalizing on it using a full-stack method.

Nvidia (NASDAQ: NVDA) stock hit a new all-time high Monday morning, shaking off its mid-December slump and jumping as much as 5.3%. As of 1:19 p.m. ET, the stock was still up 4.7%. There were a couple of developments that sent the artificial intelligence (AI) chipmaker higher,