The document discusses threads and multithreading in Java. It defines a thread as a single sequential flow of control within a program. Multithreading allows a program to be divided into multiple subprograms that can run concurrently. Threads have various states like newborn, runnable, running, blocked, and dead. The key methods for managing threads include start(), sleep(), yield(), join(), wait(), notify(). Synchronization is needed when multiple threads access shared resources to prevent inconsistencies. Deadlocks can occur when threads wait indefinitely for each other.