\- (discretionary hyphen)

Tell LaTeX that it may hyphenate the word at that point. When you insert \- commands in a word, the word will only be hyphenated at those points and not at any of the hyphenation points that LaTeX might otherwise have chosen. This command is robust (see \protect).

LaTeX is good at hyphenating and usually finds most of the correct hyphenation points, while almost never using an incorrect one. The \- command is for exceptional cases.

For example, LaTeX does not ordinarily hyphenate words containing a hyphen. Below, the long and hyphenated word means LaTeX has to put in unacceptably large spaces to set the narrow column.

\begin{tabular}{rp{1.75in}}
  Isaac Asimov &The strain of
               anti-intellectualism
               % an\-ti-in\-tel\-lec\-tu\-al\-ism
               has been a constant thread winding its way through our
               political and cultural life, nurtured by
               the false notion that democracy means that
               `my ignorance is just as good as your knowledge'.
\end{tabular}

Commenting out the third line and uncommenting the fourth makes a much better fit.

The \- command only allows LaTeX to break there, it does not require that it break there. You can insist on a split with something like Hef-\linebreak feron. Of course, if you later change the text then this forced break may look very odd, so this approach requires care.