Definition - What does Thread mean?
A thread is the smallest unit of processing that can be performed in an OS. In most modern operating systems, a thread exists within a process - that is, a single process may contain multiple threads.
Techopedia explains Thread
You can imagine multitasking as something that allows processes to run concurrently, while multithreading allows sub-processes to run concurrently.
When multiple threads are running concurrently, this is known as multithreading, which is similar to multitasking. Basically, an operating system with multitasking capabilities allows programs (or processes) to run seemingly at the same time. On the other hand, a single program with multithreading capabilities allows individual sub-processes (or threads) to run seemingly at the same time.
One example of multithreading is downloading a video while playing it at the same time. Multithreading is also used extensively in computer-generated animation.
Among the widely-used programming languages that allow developers to work on threads in their program source code are Java, Python and .NET.