Check out this link dealing with the same topic. You can also seach for "Jsp Servlet better" for more of the same. Basically they may be the same internally, but each has its own purpose. If you still have questions after checking out the links, post again.
“Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning.” - Rich Cook