This document provides an overview of threads and processes. It defines a process as an executable file and thread as a function within a process. Each process has its own address space and resources, while each thread has its own program counter, stack, and registers. It discusses single-threaded and multi-threaded processes, as well as user space and kernel space. The document also covers concurrency on single-core and multi-core systems, different threading models (many-to-one, one-to-one, many-to-many), and benefits of multi-threading like responsiveness and resource sharing. Finally, it briefly discusses user threads, kernel threads, and common thread libraries.