How to do Forecasting of Financials ?

I'm learning this from youtube videos.

Two methods of taking forecast : 

1. Through Formula 

In this we use =forecast(Xs,knownYs,knowYs)

Eg : In this we will already had data till 2024, we had put in the formula =forecast(2025,Revenue (2019:2024), Year (2019:2024))

2. Forecast on the Data Tab !

We have taken the same data as the 1st formula !

These are for one line data and provide very accurate answers, but for more and better data one need to understand the technicality of growth and it's rate.