Best way to save data

Hello, I’ve been wondering… What’s the best way to save data in games?
Maybe with JSONs? If so, how do I use it. The only way I ever saved data was making many .txt files and each of them store data then for example, let’s say I wanted to save the variable “currentWood”. I would write to a text file the “currentWood.ToString();”, I would load it by reading from the text file and converting the string to an int. But it was way too many since I was making a survival game and I had to make a text file for each variable. (example: currentWood, currentAxe, currentStone, currentMeat, etc).
So… what’s the best way to save data?

this is completely builtin to unity and very easy to use

1000s of QA on here about it, enjoy