Why Do Discs Have Holes In Them?

I only found limited results for this topic, but I think I get it. (Actually, I only got one result)

When you close the tray (the thing you put your disc on) or insert it, a small head comes out, lifts it and spins it so it can be read by a laser. It's quite simple actually.

This is where I got my answer
Learn More About CDs

While we're at the topic, I also found about the Differences Between CDs and DVDs.

CD means Compact Disc, while DVD means Digital Versatile Disc.


A CD has less storage than the DVD. A common CD can hold around eighty minutes of high-quality audio and about sixty minutes of video, while a DVD can hold up to 17 GB.

People usually use CDs for music and DVDs for movies.

The transfer rate for a CD is around 150 kilobytes per second, while a DVD's is seven times greater [which makes...1050 KB!]


Lastly, a DVD can store video, audio, data or any combination of the three, but the CD has less storage ability.


Additional Fact: A DVD player can play both CDs and DVDs, but a CD player can only play CDs.


Know More About Their Differences Here!
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A Detailed Explanation Here!

Or if you would want to know about: 


DVDs, SVCD, CD-ROMs, CD-Rs, CD-RWs, or VCDs.