Plz what's the difference b/w java phones n symbian phones. Which apps are used in developing them?

Well Symbian is an open source OS that is used by Nokia for their series 60 and series 90 range of smart phones. For development of applications that will run on Symbian devices, the S60 platform , which is open source, enables developers to develop applications and services in Java (J2ME)and even adobe's flash.

As for Java, I wont go as far as saying that Java has a mobile OS,  but the Android mobile operating system is based on Java. Although this OS is Java based it does not directly support J2ME , the reason being that the Android is more or less an alternative to J2ME. To build applications or services on the Android platform you will need to use the Android SDK which is free as it is also an open source platform.

However if you want to design a single mobile application/service (most likely Java based) that will run on both Android and Symbian operating systems, you would have to use the latest  J2ME SDK that has support for J2ME to Android Bridge adaptors (J2AB).

The Symbian is Much Complicated than that it runs various technoliges
1.Flash Lite For Mobile
2.Nokia WRT(Widget runtime Technologies)Html,css,js
3.SymbianC++ Codes will be phased out soon
4.QT C++ The new framework
5.J2ME
6.Python for symbian
7.Silverlight(Soon)
To Create Apps you will need Nokia SDK Qt to build apps for future devices N8 upwards
To Create Apps for Older Phones you need Nokia SDK for Carbide C++ (this is much harder since no one knows SymbianC++ Qt is easier)