What is the 3 richest company in the world?

Could you please enlighten me on the subject of the three wealthiest companies globally? I'm quite curious to know which organizations hold the top spots in terms of financial worth. Could you possibly provide a brief overview of these companies, perhaps highlighting their primary businesses, the industries they operate in, and any notable achievements or milestones they have reached? Additionally, I'm also interested in understanding how these rankings are determined and if there are any significant factors that contribute to their financial success. Thank you for your assistance in satisfying my curiosity.