| Words | Explanation |
| Context | A context is the contents of a CPU’s registers and program counter at any point in time. |
| Process | A process (also sometimes referred to as a task) is an executing/ running instance of a program. |
| Threads | Threads are lightweight processes that can run in parallel and share an address space (i.e., a range of memory locations) and other resources with their parent processes (i.e., the processes that created them). |
| Register | A register is a small amount of very fast memory inside of a CPU (as opposed to the slower RAM main memory outside of the CPU) that is used to speed the execution of computer programs by providing quick access to commonly used values, generally those in the midst of a calculation. |
| Program Counter | A program counter is a specialized register that indicates the position of the CPU in its instruction sequence and which holds either the address of the instruction being executed or the address of the next instruction to be executed, depending on the specific system. |
| System Call | A system call is a request in a Unix-like operating system by an active process (i.e., a process currently progressing in the CPU) for a service performed by the kernel, such as input/output (I/O) or process creation (i.e., creation of a new process). |
| Program Control Block | The state of the process includes all the registers that the process may be using, especially the program counter, plus any other operating system specific data that may be necessary. This data is usually stored in a data structure called a process control block (PCB), or switchframe. |
| ISR | Interrupt Service Routine |
| IRQ | Interrupt Request |
| URL | Uniform Resource Locators |
| CGI | Common Gateway Interface |