Java is a (object-oriented) programming language. It is a computing platform widely used for development of:
- Standalone desktop applications
- Android apps
- Online games
- Apps for Internet of things (and the like)
- Java SE (Standard Edition)
- Java EE (Enterprise Edition)
- Java ME (Micro Edition)
Java EE is a superset of Java SE. Crudely speaking, it is used in development of (complex) enterprise applications. Note that Core Java is only used for developing business logic. Other requirements include returning a dynamic response to the user, security, scalability and communication with a database etc.
Java ME is a subset of Java SE. It is used for developing applications for small-footprint devices (those with huge constraints on power and memory) like CD players and PDA's.