What is the difference between a thread/process/task?

Question

What is the difference between a thread/process/task?

Answer 1

Wikipedia sums it up quite nicely:

Threads compared with processes

Threads differ from traditional multitasking operating system processes in that:

• processes are typically independent, while threads exist as subsets of a process
• processes carry considerable state information, whereas multiple threads within a process share state as well as memory and other resources
• processes have separate address spaces, whereas threads share their address space
• processes interact only through system-provided inter-process communication mechanisms.
• Context switching between threads in the same process is typically faster than context switching between processes.

Systems like Windows NT and OS/2 are said to have "cheap" threads and "expensive" processes; in other operating systems there is not so great a difference except the cost of address space switch which implies a TLB flush.

Task and process are used synonymously.