Shell

The Shell is the core command-line interpreter: it executes user commands, manages system processes, and runs scripts (e.g., Bash) to automate complex operations.

The Shell acts as the critical interface between a user and the operating system kernel, accepting human-readable commands—like `ls`, `cd`, or `grep`—and translating them for execution. This technology is a powerful macro processor and a full programming language, supporting variables, control flow (if/then/else), and functions. The most prevalent example is the GNU Bourne-Again SHell (Bash), which is the default on most Linux and macOS systems; it’s widely used for system administration, software development, and automating tasks via shell scripts.

https://www.gnu.org/software/bash/