The basic unit of program execution. compromise of : thread ID, a program counter(PC), register sets a stack

Allow all tasks to have some progress

Perform more than one task Simultaneously 

Identifies performance gains from adding additional cores to an application that has both serial and parallel components

Distributes subsets of the same data across multiple cores, same operation on each

Multiple tasks making progress

Multithreading model where multiple user threads are mapped to a single kernel thread

There is one program counter, and one sequence of instructions that can be carried out at any given time. So only one part of the program actually can run at a time.