Underlying the original “Bell Labs” UNIX was the unifying principle of
building small powerful programs that could be connected together to
form larger workflows. The shell, where you type commands, provided
primitives such as pipes to enable such meta-level programming, and
thus it became easy to string together programs to accomplish a bigger
task. For example, to find lines of a text file that have the word
“foo” in them, and then to count how many such lines exist, you would
type: grep foo file.txt|wc -l, thus using the grep and wc (word
count) programs to achieve your task.