Define about the The .class Selector.

The .class Selector

The jQuery class selector finds elements with a specific class.
To find elements with a specific class, write a period character, followed by the name of the class:

$(".test")

Example
When a user clicks on a button, the elements with class="test" will be hidden:

Example

$(document).ready(function(){
    $("button").click(function(){
        $(".test").hide();
    });
});