jQuery append() vs appendChild()

The main difference is that appendChild is a DOM method and append is a jQuery method. The second one uses the first as you can see on jQuery source code

append: function() {
    return this.domManip(arguments, true, function( elem ) {
        if ( this.nodeType === 1 || this.nodeType === 11 || this.nodeType === 9 ) {
            this.appendChild( elem );
        }
    });
},

If you’re using jQuery library on your project, you’ll be safe always using append when adding elements to the page.