The Directory Stack (Bash Reference Manual)

6.8 The Directory Stack

The directory stack is a list of recently-visited directories. The pushd builtin adds directories to the stack as it changes the current directory, and the popd builtin removes specified directories from the stack and changes the current directory to the directory removed. The dirs builtin displays the contents of the directory stack. The current directory is always the "top" of the directory stack.

The contents of the directory stack are also visible as the value of the DIRSTACK shell variable.