Apache webserver = webserver
Tomcat =
servlet container, but some say 'application server' since it hosts 'web applications'.
Since you can host web resources such as HTML, gif, css etc. from Tomcat as well, tomcat can be used as both, but it is primarily servlet engine (or, an application server).
== <br />Rgrds,<br />Eelco<br /> <br />SCJP, SCJD, SCBCD, SCWD, SCEA