In TPU lingo, the idea that the cursor is "bound" to live between the start of line and the end of text on a line is configurable. In "unbound" mode, the cursor can move anywhere on the screen. The editor simply inserts spaces as needed to compensate for what would otherwise be a "hole" in the line.
In GnuEmacs, this can only be accomplished in PictureMode?.
In VI, there is no equivalent. Note: Can VIM do this? Answer: Easily.
The Windows based, Zeus editor does not have this limitation. It will let the cursor move past the end of line.