Cursoe function

[emmaareitch]

What does the cursor arrow actually do when a particular part of the screen is clicked on? That is, inside the circuitry, etc?

[rekstout]

If you are talking about an on-screen mouse pointer (usually an arrow of some sort) then this is a simplistic explanation

Everything you see on the screen is output from the computer - the mouse pointer is displayed by the computer interpreting input from the mouse in terms of X and Y co-ordinates.
The screen is composed of a very fine grid of dots called pixels, the co-ordinates of which are known by the computer.
When you move the mouse, the computer calculates the equivalent move in pixels and re-displays the mouse pointer in the new position.
When the you click on the mouse button, the computer knows where the pointer is and knows what pixels are beneath the pointer, depending upon what the pixels underneath the mouse are designed to represent, different actions will be performed by the computer.
For example ' if the pixels at certain co-ordinates represent a 'Send' button for an email program, the computer will know to perform the 'send' action.

I hope that is comprehensible!

[xyzzyplugh]

And collision detection; in the same way the bat knew it had hit the ball back in the days of Pong. But very succinctly put rekstout. - So how do the search engines read millions of pages in a couple of seconds? especially the ones that read content within the pages?