Application server serves applications .It creates dynamic
web pages .It supports services like
transaction ,security .It provides container for
Servlets,Jsp engine ,ejb container ..e.g. BEA weblogic ,
IBM websphere
Web server is one who serves HTTPs, It can create static
web pages .It supports services like load balancing ,
clustering ...
database server supports db activies it manages db
transactions in multitier web applications .e.g oracle ,db2
tomcat is web server + servlet container
it dose not support ejbs and jms