A cursor is a pointer which indicates the position of the mouse on a computer's display monitor.
An insertion point is a location in a document where additional information is inserted when the user begins to type.
A mouse pointer is an image used to activate/control certain elements in a GUI (graphical user interface).
I know you asked for the differences, though i thought I'd add a similarity. All of these 3 things are similar, as they show where the position of the info/mouse is. :)
