Makes Vim work in a way that Insert mode is the default mode. Useful if you want to use Vim as a modeless editor. Used for |evim|. These Insert mode commands will be useful:

• Use the cursor keys to move around.
• Use CTRL-O to execute one Normal mode command |i_CTRL-O|. When this is a mapping, it is executed as if 'insertmode' was off. Normal mode remains active until the mapping is finished.
• Use CTRL-L to execute a number of Normal mode commands, then use to get back to Insert mode. Note that CTRL-L moves the cursor left, like does when 'insertmode' isn't set. |i_CTRL-L|