What is the Fortran language used for? [closed]

It serves for the same as the other high level languages, it allows a human to write algorithm such that after interpreted by some application (compiler or interpreter) it becomes instructions that the machine understands and executes that algorithm producing computational results.

Since it was the first high-level language to be created, its main asset was to allow for an easier and simpler way of writing code, avoiding some errors that were very common in Assembly.

Since the beginning of computing only imported calculations, it was thought to facilitate this and to this day it is seen as strong in complex numerical manipulations, especially with data vectors. Today it has several optimizations for it and by having limitations in other points can focus on that part.

Of course it does a lot of other things like any programming language, but it's very good at it and it gets faster than C in some operations. And it does not have the idiosyncrasies of handling mechanisms that C has.