A thread in Java is the smallest unit of a process that can be scheduled for execution. It represents the path of execution within a program, allowing the program to operate more efficiently by doing multiple things at the same time. In Java, all programs have at least one thread, known as the main thread, which is provided by the Java Virtual Machine (JVM) at the start of the program's execution. Additional threads can be created to run concurrently with the main thread, allowing for parallel execution of tasks. Threads can be created by extending the Thread class or implementing the Runnable interface. They have their own program counter, stack, and local variables, and each thread is assigned a priority that influences its order of execution. Multithreading in Java is used to maximize CPU utilization and is often referred to as concurrency in Java