Child theme theme folder: get_stylesheet_directory_uri()

    ex: https://trumpetvine-framework.com/wp-content/themes/trumpetvine-child

Parent theme theme folder: get_template_directory_uri()

    ex: https://trumpetvine-framework.com/wp-content/themes/trumpetvine-framework

Domain root: "http(s)://".$_SERVER['SERVER_NAME']

    ex: https://trumpetvine-framework.com

WordPress root:

    site_url(); ex: https://trumpetvine-framework.com

WordPress admin:

    admin_url(); ex: https://trumpetvine-framework.com/wp-admin/

Just the domain $_SERVER['SERVER_NAME']

ex: trumpetvine-framework.com