By default, jQuery won't be added to your website. However, if you are going to use the Visual (WYSIWYG) editor you need jQuery implemented on your website. If you do not have that it can be added through Symplify.
To do this go to My websites -> click the website -> select Edit website -> check Add jQuery to website and click Save
Notice! If you are not sure if it is safe to add jQuery you should talk to your developers before doing so.