jQuery difference between .add() and .append()

.add()

Add elements to the set of matched elements.

$('div').css('background-color':'yellow').add('p').css('color':'red');

.append()

Insert content, specified by the parameter, to the end of each element in the set of matched elements.

$('div').append('p');

Reference: whats-the-difference-between-add-and-append-jquery