A thread is a thread of execution in a program. The Java Virtual Machine allows an application to have multiple threads of execution running concurrently.
Simply put, a thread is a program's path of execution. Most programs written today run as a single thread, causing problems when multiple events or actions need to occur at the same time. Let's say, for example, a program is not capable of drawing pictures while reading keystrokes. The program must give its full attention to the keyboard input lacking the ability to handle more than one event at a time. The ideal solution to this problem is the seamless execution of two or more sections of a program at the same time. Threads allows us to do this.
import java.lang.*;
public class Counter extends Thread
{
public void run()
{
....
}
}

Synchronization is best use with the Multi-Threading in Java, Synchronization is the capability to control the access of multiple threads to share resources. Without synchronization it is possible for one thread to modify a shared object while another thread is in the process of using or updating that object's value.This often leads to an error.

Example for Synchronization
public synchronized void enqueue(Object item)
{
// Body of method goes here

}

shorthand notation for
public void enqueue(Object item)
{
synchronized (this)
{
//Body of method goes here
}
}

Hi Friend,

A thread is light weighted process which exist within a program and executed to perform a special task.

Synchronization is a process of controlling the access of shared resources by the multiple threads in such a manner that only one thread can access a particular resource at a time.

For more information, visit the following link:

http://www.roseindia.net/java/thread/index.shtml

Thanks