The shell is a command interpreter. More than just the insulating layer between the operating system kernel and the user, it's also a fairly powerful programming language. A shell program, called a script, is an easy-to-use tool for building applications by "gluing together" system calls, tools, utilities, and compiled binaries.
Shell是一種命令直譯器。其角色不僅是作業系統核心與使用者間的翻譯者，也是一種強大的程式語言。Shell程式，通稱為「腳本」，是一種容易上手的工具，其結合了系統呼叫、工具及一些編譯好的二進制執行檔。
Virtually the entire repertoire of UNIX commands, utilities, and tools is available for invocation by a shell script. If that were not enough, internal shell commands, such as testing and loop constructs, lend additional power and flexibility to scripts.
基本上，幾乎所有的工具與Linux系統的指令都可以在shell腳本內被使用、呼叫。如果還想讓shell腳本發揮更大效用，則可搭配shell命令，例如：迴圈或測試相關指令。
Shell scripts are especially well suited for administrative system tasks and other routine repetitive tasks not requiring the bells and whistles of a full-blown tightly structured programming language.
簡言之，shell腳本是特別為系統管理者量身定做的程式語言。