$(".class").click(function(){
$(this).find(".subclass").css("visibility","visible");
});
$('.your_class_name')
$(".className")
$('.class').jquery_function();
document.querySelector('h1');
//basically the $ = document.querySelector()
//below is the equivalent to above
$('h1'); // by element
$('.by-class');
$('#by-id');
$('.classid')