AJAX stands for Asynchronous JavaScript And XML.
Ajax is based on JavaScript language, besides it uses HTML, CSS and a language for the server-side (like PHP or ASP).
The AJAX lessons in this course are free and best suited for beginners, it offers the necessary elements to learn Ajax and work with it. But you need to know, at least at a beginner level, PHP and JavaScript.
<input type="checkbox" name="a_name" value="value" checked="checked" />
#id { background:url("path_to_image.png"); background-size:contain; background-repeat:no-repeat; }
var rest8_7 = 8 % 7; alert(rest8_7);
$nr = ceil(3.5); echo $nr; // 4