Website development broadly refers to the tasks associated with developing websites for hosting via intranet or Internet. The Web development process includes Web design, Web content development, client-side/server-side scripting and network security configuration, among other tasks.
PHP (originally short for Personal Home Pages, and now oddly considered short for PHP Hypertext Preprocessor) is a popular scripting language that is embedded into HTML pages. What’s great about PHP is that it is open source, which means that it is free to use, and people who build cool functions with it often make their code available for free as well. This results in an ever-increasing library of PHP code modules that you can utilize to enhance your site. Facebook, for example, was built from the ground up largely using PHP.
ASP.NET (a-s-p-dot-net) is a proprietary Microsoft platform designed for developing web applications. Though it is not free, there is a large library that covers a lot of basic functions and database interactions that makes the programmer’s job easier, and the library comes with full technical support. A major difference from something like PHP code, is that ASP.NET code must be compiled (converted into an executable file) in order to utilize it in your website. Compiled code is said to perform faster and be more secure since you cannot see the source code embedded in the HTML. The other advantage is that .NET is fairly ubiquitous; there are a lot of engineers that know how to build .NET applications, and so you will never be short on resources.
JSP (Java Server Pages) is a web development platform introduced by Sun Microsystems (now part of Oracle) to compete with PHP and ASP.NET. Like ASP, it is a server-side technology, meaning that the code is first compiled and then executed as an application by the web server.