The Sun Java Wireless Toolkit is also known as Java Platform, Micro Edition (Java ME) Wireless Toolkit. Java Platform, Micro Edition or Java ME was previously known as Java 2 Platform, Micro Edition or J2ME). It is a specification of a subset of the Java platform that focuses on to provide a certified collection of Java APIs for the development of software for small, resource-constrained devices such as cell phones, PDAs and set-top boxes. It is a specification of a subset of the Java platform to develop wireless applications based on Mobile Information Device Profile (MIDP),  J2ME's Connected Limited Device Configuration (CLDC), such as cell phones, PDAs, set-top boxes and  designed to run on cell phones, mainstream personal digital assistants, and many other small mobile devices. The toolkit also consists emulation environments, performance optimization, tuning features, documentation, and examples required by the developer to develop efficient and successful wireless applications to market quickly. Sun Microsystems develop this (Java ME) as a replacement for a similar technology, Personal Java.

Connected Limited Device Configuration (CLDC): It is a subset of the Java class libraries that mainly classifies myriad devices into a fixed configuration. A configuration provides the most basic set of libraries and virtual-machine features that each Java ME must contain.
 
Mobile Information Device Profile: Applications developed by using with this profile are known as MIDlets. Today almost all the cellphones comes with MIDP implementation. Now it has become the de facto standard to download the cell phone games.
 
Information Module Profile (IMP): IMP applications are known as IMlets, but in fact they are MIDlets. They have the same packaging style, deployment, life-cycle as MIDlets and security.
    
Connected Device Configuration: It is a subset of Java SE that includes almost all the non GUI related libraries. It is more rich as compairing to CLDC.