HTML5 was developed to solve compatibility problems that affect the current standard, HTML4.
CSS3 is the latest version of the CSS specification. The term “CSS3” is not just a reference to the new features in CSS, but the third level in the progress of the CSS specification.
If you have any sort of interest in web development, you’ve likely heard of Bootstrap.
Since you've come to this page, you may already have a pretty good idea about what jQuery is, but to be on the safe side, here is a brief explanation.
PHP is a language that is specifically designed for web programming with built-in integration with the most popular open source database MySQL.