A Thread pool is a collection of threads. These threads can be used to perform tasks without disturbing the primary thread. Once the thread completes the task, the thread returns to the pool.
System.Threading.ThreadPool namespace has classes which manage the threads in the pool and its operations.
System.Threading.ThreadPool.QueueUserWorkItem(new System.Threading.WaitCallback(SomeTask));
The above line queues a task. SomeTask methods should have a parameter of type Object.
