They are child processes.

Second answer: Linux doesn't differentiate between threads and processes. It has a "thread group ID" that serves a small number of purposes, and the rest of the difference is just whether the threads happen to share the same address space.

Actually on Windows a process is a thread with additional information.

The unit of execution is the thread.

On the UNIX world it depends on which UNIX you are talking about.

Linux has a similar model to Windows NT nowadays, hence clone() as key primitive.

Other UNIXes have different approaches.