Overtype mode is an editing mode in a word processor, in which typed characters directly replace the character immediately following the cursor. When overwrite mode is turned off, characters are inserted at the cursor position.
The easiest way to determine whether overwrite mode is turned on is to type a character with the cursor behind another character. If it directly replaces the character, overwrite mode is on. Overwrite mode can be turned on and off using the insert key, often labeled INS. Typically, an indicator on the status bar, normally at the bottom right corner of the word processor, indicates this with the letters OVR. In some word processors, clicking on the indicator on the status bar also turns overwrite mode on and off.
Modern word processors operate in insert mode by default. If this feature is frustrating, overtype mode can be completely disabled in Word 2010 and 2013 by clicking on File, Options, choosing Advanced on the left, and unchecking the boxes that say, "Use the insert key to control overtype mode" and "Use overtype mode."
On early text-based environments, overtype mode was indicated by the cursor displaying as a block highlighting a character. Insert mode was indicated by a vertical bar between characters.