Insert, Overwrite, Change

In VIM you have a variety of ways to start entering text, as mentioned above in the section on Modality.

You are normally in command mode. When you type certain keys, you are placed in insert mode or overtype mode. In insert mode, the text you type goes before the cursor position, and everything after the cursor is pushed to the right or to the next line.

In overtype mode your keystrokes are input, just as they are in insert mode, but instead of inserting the keystrokes VIM will replace the next character in the document with the character you type. You get to overtype mode by pressing an overtype key command while in command mode.

In ex mode you are typing a string of commands to run into a little window at the bottom of the screen. We'll talk about this later on, because it's powerful stuff. It's also a little cryptic, so we will wait.

You get into ex mode by typing ":" in command mode.

You always return to command mode from overtype, insert, or command mode by pressing escape.

That is one handy key.

i	insert before the current cursor position
I	insert at the beginning of the current line. Far better than pressing ^ and then i.
a	insert after the current cursor position
A	insert/append at the end of the current line. Far better than pressing $ and then i.
r	retype just the character under the cursor
R	Enter overtype (replace) mode, where you destructively retype everything until you press ESC.
s	(substitute) delete the character (letter, number, punctuation, space, etc) under the cursor, and enter insert mode
c	the 'change' (retype) command. Follow with a movement command. cw is a favorite, as is cc
C	Like 'c', but for the entire line.
o	insert in a new line below the current line
O	insert in a new line above the current line
:	Enter command mode (for the advanced student)
!	Enter shell filter mode (for the very advanced student)

Consider the value of the c command. If you use it with the t or f commands, it becomes very powerful.

If you were at the C at the beginning of the previous sentence, you could type ct. and retype the whole first sentence, preserving the period.

The same is true with other commands, such as the d for delete.

The movement commands add a lot of power to the change command, and that's one reason why it is important to learn to move well.