In normal text, the \- command tells LaTeX that it may hyphenate the word at that point. LaTeX is very good at hyphenating, and it will usually find all correct hyphenation points. The \- command is used for the exceptional cases.
In the tabbing environment, the \- command moves the left margin of the next and all the following commands one tab stop to the left.
See also: Environments, tabbing, Line and Page Breaking,