when the insert
     started.
"v"  Only break at a white character that has been entered during the
     current insert command.  This is mostly Vi-compatible.
"lv" Only break if the line was not longer than 'textwidth' when the insert
     started and only at a white character that has been entered during the
     current insert command.  Only differs from "l" when entering non-white
     characters while crossing the 'textwidth' boundary.

Normally an internal function will be used to decide where to break the line.
If you want to do it in a different way set the 'formatexpr' option to an
expression that will take care of the line break.

If you want to format a block of text, you can use the "gq" operator.  Type
"gq" and a movement command to move the cursor to the end of the block.  In
many cases, the command "gq}" will do what you want (format until the end of
paragraph).  Alternatively, you can use "gqap", which will format the whole
paragraph, no matter where the cursor currently is.  Or you can use Visual
mode: hit "v", move to the end of the block, and type "gq".  See also |gq|.

==============================================================================
4. 'expandtab', 'softtabstop' and 'smarttab' options	*ins-expandtab*

If the 'expandtab' option is on, spaces will be used to fill the amount of
whitespace of the tab.  If you want to enter a real <Tab>, type CTRL-V first
(use CTRL-Q when CTRL-V is mapped |i_CTRL-Q|).
The 'expandtab' option is off by default.  Note that in Replace mode, a single
character is replaced with several spaces.  The result of this is that the
number of characters in the line increases.  Backspacing will delete one
space at a time.  The original character will be put back for only one space
that you backspace over (the last one).

							*ins-softtabstop*
When the 'softtabstop' option is non-zero, a <Tab> inserts 'softtabstop'
positions, and a <BS> used to delete white space, will delete 'softtabstop'
positions.  This feels like 'tabstop' was set to 'softtabstop', but a real
<Tab> character still takes 'tabstop' positions, so your file will still look
correct when used by other applications.

If 'softtabstop' is non-zero, a <BS> will try to delete as much white space to
move to the previous 'softtabstop' position, except when the previously
inserted character is a space, then it will only delete the character before
the cursor.  Otherwise you cannot always delete a single character before the
cursor.  You will have to delete 'softtabstop' characters first, and then type
extra spaces to get where you want to be.

							*ins-smarttab*
When the 'smarttab' option is on, the <Tab> key indents by 'shiftwidth' if the
cursor is in leading whitespace.  The <BS> key has the opposite effect. This
behaves as if 'softtabstop' were set to the value of 'shiftwidth'. This option
allows the user to set 'softtabstop' to a value other than 'shiftwidth' and
still use the <Tab> key for indentation.

==============================================================================
5. Replace mode				*Replace* *Replace-mode* *mode-replace*

Enter Replace mode with the "R" command in normal mode.

In Replace mode, one character in the line is deleted for every character you
type.  If there is no character to delete (at the end of the line), the
typed character is appended (as in Insert mode).  Thus the number of
characters in a line stays the same until you get to the end of the line.
If a <NL> is typed, a line break is inserted and no character is deleted.

Be careful with <Tab> characters.  If you type a normal printing character in
its place, the number of characters is still the same, but the number of
columns will become smaller.

If you delete characters in Replace mode (with <BS>, CTRL-W, or CTRL-U), what
happens is that you delete the changes.  The characters that were replaced
are restored.  If you had typed past the existing text, the characters you
added are deleted.  This is effectively a character-at-a-time