This option changes how text is displayed. It doesn't change the text in the buffer, see 'textwidth' for that. When on, lines longer than the width of the window will wrap and displaying continues on the next line. When off lines will not wrap and only part of long lines will be displayed. When the cursor is moved to a part that is not shown, the screen will scroll horizontally. The line will be broken in the middle of a word if necessary. See 'linebreak' to get the break at a word boundary. To make scrolling horizontally a bit more useful, try this:

:set sidescroll=5
:set listchars+=precedes:<,extends:>

See 'sidescroll', 'listchars' and wrap-off. This option can't be set from a modeline when the 'diff' option is on.

(default on)