Org is an Emacs mode for keeping notes, maintaining TODO lists, and project planning with a fast and effective lightweight markup language. It also is an authoring system with unique support for literate programming and reproducible research. If you work with the LaTeX output capabilities of Org-mode, you may want to install the emacs-org-texlive-collection meta-package, which propagates the TexLive components required by the produced .tex file.