What is the Mouse Cursor?
The mouse cursor is a small floating icon on the screen, typically a white diagonal arrow, that indicates the position of the mouse on the screen. As you move the mouse across the desk, the mouse cursor moves accordingly.
More technically, on a screen with a resolution of 1600 pixels of width by 900 pixels of height, for example, the mouse cursor actually has the size of exactly 1x1px, although the icon that you see may be much larger than that. In other words, the mouse cursor is just one single pixel on the screen that you control using the mouse.
The term cursor is sometimes used to refer to the icon displayed where the cursor is. Since the cursor is actually only 1 pixel in size, it can be very difficult to tell where this pixel is on the screen if it was actually just one colored pixel moving around. To remedy this, the "cursor icon" is typically much bigger and taller, which means only one single pixel on this cursor is the actual effective area of the cursor.
For example, the default cursor icon is a diagonal white arrow that points toward the top-left corner of the screen. The 1x1px "cursor" on this icon is actually on the very tip of the arrow. Not on the middle, nor on the tail. On the tip. This means you can't click on something by placing the tail of the arrow over it while the tip of the arrow is over something else, because it's only the tip that counts.
In most systems, it's possible to customize the appearance of the cursor icon. The cursor icon image format is special, and has a .cur file extension. The special property of this format is that it stores a "hot spot" coordinate that indicates where the actual cursor pixel is. For example, in an arrow icon, the hot spot would be set to the arrow tip. In a hourglass icon, the hot spot is normally at the center. The cursor icon is displayed on the screen so that this "hot spot" in the cursor image matches the actual cursor pixel that the system uses to decide what graphical user interface elements the mouse is currently hovering over.
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