• • ServletConfig is an in-built interface preasent in javax.servlet.*; package
• • ServletConfig object is one per servlet class
• • ServletConfig object will be created during initialization process of the servlet
• • This object is public to a particular servlet only
• • Scope: As long as a servlet is executing, ServletConfig object will be available, it will be destroyed once the servlet execution is completed.
• • We should give request explicitly, in order to create ServletConfig object for the first time
• • In web.xml <init-param> tag will be appear under <servlet-class> tag

Here's how it looks under web.xml :

ServletContext

• • ServletContext interface available in javax.servlet.*; package
• • ServletContext object is global to entire web application
• • Object of ServletContext will be created at the time of web application deployment
• • Scope: As long as web application is executing, ServletContext object will be available, and it will be destroyed once the application is removed from the server.
• • ServletContext object will be available even before giving the first request In web.xml <context-param> tag will be appear under <web-app> tag

Here's how it looks under web.xml :

So finally...

No. of web applications = That many number of ServletContext objects

No. of servlet classes = That many number of ServletConfig objects

Difference between ServletContext and ServletConfig