JSP are java server pages which constitute of html pages 
embedded in it ie it is useful for both presentation and 
application/business logic..It is compiled only once and 
each time it is not executed by server..While servlet are 
server side programs which are compiled  and is executed
each time..

jsp means java server page ,jsp is  laso a servelt .In the 
servlet code is written by manually but in jsp code is 
generated by the jsp container. 
jsp is used where the presentation layer is more, and  this 
is uesd in medium and larger projects
servlet is used in small projects

adv:
 1. jsp can be devolp easly.
 2. jsp will take less time.
disadv:
  1. it can accupi the more memory(why because it fallow 
structural procedure menas by genearting the servlet code 
included unnecessry content also)

>Servlets are gud at running logic.
>not so gud at producing large amount of o/p.

>Not so gud at lots of logic.
>g8 ay producing lots of texual o/p.

Jsp is defined as Java server pages. 
Jsp and servlet both are server side programming language. 
the diffence in b/w these two is Jsp is used for 
presentation part and servlet is use to give the business 
logic. 
Servlet act as redirector also. it redirect your page as 
per the business logic. 

anyhow Jsp are compiled to servlet but Jsp comes in to 
picture to separate out the presentation logic from the 
servlet to make it loosely coupled.

Servlets and Java Server Pages are complementary APIs, both
providing a means for generating dynamic Web content. A
servlet is a Java class implementing the
javax.servlet.Servlet interface that runs within a Web or
application server's servlet engine, servicing client
requests forwarded to it through the server. A Java Server
Page is a slightly more complicated beast. JSP pages contain
a mixture of HTML, Java scripts (not to be confused with
JavaScript), JSP elements, and JSP directives. The elements
in a Java Server Page will generally be compiled by the JSP
engine into a servlet, but the JSP specification only
requires that the JSP page execution entity follow the
Servlet Protocol.

The advantage of Java Server Pages is that they are
document-centric. Servlets, on the other hand, look and act
like programs. A Java Server Page can contain Java program
fragments that instantiate and execute Java classes, but
these occur inside an HTML template file and are primarily
used to generate dynamic content. Some of the JSP
functionality can be achieved on the client, using
JavaScript. The power of JSP is that it is server-based and
provides a framework for Web application development. Rather
than choosing between servlets and Java Server Pages, you
will find that most non-trivial applications will want to
use a combination of JSP and servlets. In fact, the JSP 1.1
and Servlet 2.2 specifications are based around the concept
of the Web application, combining the two APIs into a
unified framework.
(http://www.devx.com/tips/Tip/25217)