'textwidth' 'tw' number (default 0)
local to buffer
{not in Vi}
Maximum width of text that is being inserted. A longer line will be
broken after white space to get this width. A zero value disables
this. 'textwidth' is set to 0 when the 'paste' option is set. When
'textwidth' is zero, 'wrapmargin' may be used. See also
'formatoptions' and |ins-textwidth|.
When 'formatexpr' is set it will be used to break the line.
NOTE: This option is set to 0 when 'compatible' is set.
'wrapmargin' 'wm' number (default 0)
local to buffer
Number of characters from the right window border where wrapping
starts. When typing text beyond this limit, an <EOL> will be inserted
and inserting continues on the next line.
Options that add a margin, such as 'number' and 'foldcolumn', cause
the text width to be further reduced. This is Vi compatible.
When 'textwidth' is non-zero, this option is not used.
See also 'formatoptions' and |ins-textwidth|. {Vi: works differently
and less usefully}