Insertion point: Indicates where thped characters will be inserted(shows as a thin line cursor).
Obsolete topic - overstrike typing mode: Word processors used to have a mode to allow you to type over text, instead of replacing. This mode is seldom used today, and is not available in all word processors. Today, instead of typing over text, you hilite it. Then what you type replaces all of the hilited text.
Insert typing mode: (the default mode) -Typed characters are inserted at the insertion point (thin line cursor), causing following characters to shift to the right.