Path for Child & Parent Theme In WP

get_stylesheet_directory()     // PATH (parent or child)
get_stylesheet_directory_uri() // URI (parent or child, checks for SSL)

get_template_directory()     // PATH (parent only)
get_template_directory_uri() // URI (parent only, checks for SSL)

References
get_stylesheet_directory() – file path to current theme directory
get_stylesheet_directory_uri() – URL to current theme directory
get_template_directory() – file path to parent theme directory
get_template_directory_uri() – URL to parent theme directory