This lets you choose between either viewing files with their actual line lengths or wrapping text to a fixed maximum line length. If the line length is changed it will only affect newly created windows not existing ones.

 

Line Length

If you select 'Normal' then each line will not be wrapped to any particular line length. For Word, HTML, RTF and Write files each paragraph is treated as a single line. Otherwise you can select 'Wrap' and specify the number of characters to wrap to, within the range 25 to 250 characters.