JSP is an acronym which stands for Java Server Page.
A JSP is essentially an HTML document that has java code or special tags included. A JSP can only be run inside a Servlet/JSP Engine.
When the Engine receives a request for a JSP, the engine will perform the following actions:
Parse the requested .jsp file and convert it into a servlet, saving the result to .java source file.
Compile the generated Servlet into a .class file.
Load the servlet class file into the JVM, instantiate an instance of the servlet and invoke the appropropriate Servlet API methods to service the request (send the response).