'innerHTML' is used in 'Searching: getElement*, querySelector*', and later DOM sections, but I don't find them explained anywhere in the tutorial. Even did a site search on Google: https://www.google.com/search?safe=off&sxsrf=ACYBGNRkjgq-Vz434fEP-NHv_XijVN4T7Q%3A1571284776662&source=hp&ei=KOenXfO_JYHYtAXK0KKgCA&q=site%3Ajavascript.info+innerHTML&oq=site%3Ajavascript.info+innerHTML&gs_l=psy-ab.3...3835.13280..13637...1.0..0.206.4398.0j30j2......0....1..gws-wiz.....9..35i362i39j35i39j0j0i131j0i10.rsBq_MCzblE&ved=0ahUKEwjz8833s6LlAhUBLK0KHUqoCIQQ4dUDCAg&uact=5 (though the Google search is obviously incomplete, not including the "Searching..." page)