What is the technical difference between a process and a thread? I get the feeling a word like 'process' is over used and there is also hardware and software threads. How about light-weight processes in languages like Erlang? Is there a definitive reason to use one term over the other?
Both processes and threads are independent sequences of execution. The typical difference is that threads (of the same process) run in a shared memory space, while processes run in separate memory spaces.
I'm not sure what "hardware" vs "software" threads might be referring to. Threads are an operating environment feature, rather than a CPU feature (though the CPU typically has operations that make threads efficient).
Erlang uses the term "process" because it does not expose a shared-memory multiprogramming model. Calling them "threads" would imply that they have shared memory.