Apache is a web server.
Apache Tomcat is a
Servlet Container, that is also capable of acting as a web server.
Many folks will integrate the two, in order to take advantage of Apache's security, management and performance features as a web server, using it to serve static content, while using Apache Tomcat to handle the dynamic content requests.
Note that Servlets and JSPs cannot be deployed to the Apache web server. For that you need a Servlet container like Apache Tomcat or Resin.
Clearer?
http://apache.org http://jakarta.apache.org/tomcat