The JVM is the core of the Java platform and is responsible for:

1. Loading bytecodes from the class files
2. Verifying the loaded byte codes
3. Linking the program with the necessary libraries 
4. Memory Management by Garbage Collection
5. Managing calls between the program and the host environment.

Java sovles the problem of platform independence by using 
byte code.Java complier does not produce native executable 
code.Instead it produces a special format called byte code.

Byte code is a highly optimized set of instructions 
designed to executed by a java runtime system called Java 
Virtual Machine(JVM).JVM is an interpreter for byte code.

This interpreter reads or understands the bytecode and 
executes the corresponding native machine instructions.

Thus to port java programs to a new platform ,all that 
needed is to port the interperter and some of the library 
routines.Even the complier is written in java.The byte 
codes are precisely defined and remain the same on all 
platforms.

The use of byte code  enables the java runtime system to 
execute programs much faster.

JVM will convert the byte code to user understandable code.
Provides the services like class loading,garbage collection