JavaScript Design Patterns: What is a Concrete Factory?

While reading about factories in this article, I came across these two terms AbstractFactory and ConcreteFactory.

While reading on StackOverflow, I found some good answers (like this SO question) that talk about factories and abstract factories, but still not clear about what a concrete factory is.

So, I wanted to ask:

1. What is a concrete factory?
2. How is it different from an abstract factory?

EDIT: Asking the question #2 in a separate question (will update link here soon).

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My understanding so far (about factories):

• At high level, I understand that, by a factory we refer to a method that returns a brand new something (can be anything, an object, a method, anything that's needed as our requirement), that we'd call a factory. Here, please correct me if I'm wrong.
• that factories encapsulate and separate object creation from the rest of your code. Below is an example to illustrate the same:

// This function is a factory. When called, creates and returns a new object every time
function ourFactoryFn (firstName, lastName) {
    var a = {
        prop1:  firstName,
        prop2: lastName,
        prop3: firstName + ' ' + lastName + ' says Hello world!'
    }
    return a;
};

// Now, let's use our factory to produce new objects
// let's actually have an example to treat it like real life factories :P
var inputArr = [
    {firstName: 'Barack', lastName: 'Obama'},
    {firstName: 'Narendra', lastName: 'Modi'},
    {firstName: 'Mike', lastName: 'Tyson'},
    {firstName: 'Mahatma', lastName: 'Gandhi'},
    {firstName: 'Donald', lastName: 'Trump'},
    {firstName: 'Priyanka', lastName: 'Chopra'}
];
var outputArr = [];
inputArr.forEach(function (x) {
    var newObj = ourFactoryFn(x.firstName, x.lastName); // we used our factory
    console.dir(newObj); // print the freshly created object
    outputArr.push(newObj);
});