"el" is a parameter of the function that is used in filter, it will save the elements of the array in each iteration of filter, so he uses "el" in the function to have each character in the array. I think he named the parameter "el" because of "element". The reason it maybe look's something weird it's because he use a "function expresion"( function(){} ) instead of a "arrow function"( () => {} )

My suggestion is that you breakdown the code by methods like the filter method.

Example: filter()

const words = ['spray', 'limit', 'elite', 'exuberant', 'destruction', 'present'];

const result = words.filter(word => word.length > 6);

console.log(result);
// expected output: Array ["exuberant", "destruction", "present"]