Pretty straightforward. The current value of the company is the Net Present Value of all the future expected cash flows. Basically you can take the money Apple will make in 2024, 2025, 2026 ... and reduce them to today's values by discounting with the interest rates: pretty much divide by (1+r)^n. Since Apple already makes a ton of money each year it is valued pretty high. Nvidia on the other hand has to GROW its earnings a LOT to justify its valuations.