Dash is a shell with POSIX features and little more. It is derived from the Almquist shell ash, originally to serve as
/bin/sh on Debian, and also used in Ubuntu and other derivatives and other Linux distributions. Dash is smaller and faster than Bash bash, but has fewer features.
Use this tag if your question is specifically about Dash. If your question is about Bourne/POSIX shells in general, use shell.