See:
Before Fortran, computer programs had to be written in assembler language, which was the native internal logic of the computer hardware. Every task had to be broken down into very structured basic steps. The programmer had to know specialized arithmetic, such as binary or octal and an intimate knowledge of the computer's internal techniques.
Every computer had its own specific internal logic, so programs written for one type of computer couldn't be run on another type. Programmers had to learn a whole new logic structure of every computer they used.
Fortran allowed programs to be written in an algebraic like language that was already familiar to engineers and scientists who were using the computer for research.
Fortran also paved the way for other languages such as BASIC and COBOL.
Fortran works by translasting the algebraic instructions into the structured basic basic steps of assembler language. To the programmer, the language remains mostly the same even on different computers by different manufacturers.
Those of us who utilize computers in our career owe a great deal to Mr. Backus (as well as Grace Hopper who developed COBOL and Kemeny and Kurtz who developed BASIC.)