What is inside the Web App?

It has been a hard time for me in last week to figure out what is inside Web Application Archive, so called WAR. I was really stressing myself in building this shit using pure ANT script. Basically this file consist of two main portion, the 1st portion storing the JSP file, whereas the 2nd portion is the WEB-INF directory. Now the interesting one, WEB-INF must contain classes (containing the compile binary of java code), lib (containing third party jar file, usually only jar), and web.xml (I don't really bother what the heck is this).