Once you have entered insert mode with any of the above commands you are able to continue typing and inserting text. "vi" will allow you to delete characters and edit within the current line you are editing but will not give you any other cursor positioning capabilities or editing functions beyond the ability to backup and delete characters and entered. In fact, if you try to use any of the cursor positioning keys, besides the [DEL] key or [CTRL-W] (used to backup over and delete words), while still in insert mode, you run the risk of losing portions of your text. Be certain that you are in command mode, not insert mode, when using the cursor positioning keys (please see the next section for a list of what these keys are).
If you need to do major editing on text, you can return to command mode by pressing the [ESC] key. You may now use all the cursor positioning commands and editing commands available in command mode.