Hello, I can’t tell what’s happening in low level that FText works how it works (it’s one of native UE variable types), but the main usage is in places where a text will be visible to the end user (so mostly texts in UI).
It is because all FTexts used in your project can be gathered by Localization Dashboard and then you can set their corresponding values in other languages.
So again, for all technical texts use FString, for all text that will be visible by end users use FText.