The key bindings in this mode is the same as in the emacs mode except for the following 4 keys. So, you can move around in the buffer and change its content while you are in insert mode.
This key will take you back to vi mode.
Delete previous character.
Delete previous word.
Typing this key has the same effect as typing ESC in emacs mode. Thus typing C-z x in insert mode will have the same effect as typing ESC x in emacs mode.