These are called line editors. The standard line-oriented editors found on UNIX systems are ed and ex. Another type of editor displays entire screens of text at one time in which the text can be edited in units larger than single lines. These are full-screen editors. Emacs and vi are the two most typical full-screen editors on UNIX systems.
Manual pages are available online for each of the editors listed above.
For example, type man vi to see the entry for vi. Manuals and reference material for these editors are on reserve at Consulting Services at Information Technology. Several have been written specifically on the document preparation system in UNIX, usually meaning vi and nroff, or troff text-formatting software. Examples can be found at the Boston University Bookstore. Information Technology offers tutorials in Emacs.