Hi,

ServletContext: ServletContext is a view of webapplication, 
there will be only one servletcontext for one 
webapplication. It acts as shared memoty area, all the 
components of a webapplication can access the data from  
servletcontext object.

ServletConfig:  ServletConfig will be specific to each 
servlet. If your webapplication contains 20 servlets then, 
there will be 20 servletsconfig objects.

Servlet Context: Servlet Context defines a set of methods
that a servlet uses to communicate with its servlet container.

Servlet Config: A servlet configuration object used by a
servlet container passes information to a servlet during
initialization.

Servlet Context -> It is one for the web application.
Servlet Config -> It is one for the Servlet.