A cursor is an indicator of positioning.
Once found on all slide rules, where it was a sliding glass or plastic plate that had a fine line etched or painted onto it to line up the different scales. Slide rule operation consists of finding a number on one scale and lining it up with a number on another scale. If the scales a separated by any distance, the cursor is used to accurately line them up or read values.
It is now more common as a feature of a computer user interface. On computers with a graphical user interface, there are two cursors: when editing text, a cursor called an insertion point is displayed to show the location of any modifications. This is usually represented by a blinking vertical line. The other cursor is the mouse pointer, usually an arrow that moves on the screen as you move the mouse on your desk.
In many computer programs, the shape of the cursor changes when the user's task changes. For instance, a text-insertion cursor is displayed while the user is writing something, or a graphics-editing cursor is displayed while the user is editing an image. When a computer is performing tasks and is unable to accept user input, a wait cursor may be displayed to indicate that the machine is unusable.
The term cursor is also used in database packages to refer to a control structure for the traversal of records returned by a query.