Digital Audio (S/PDIF) is an optical output and Speakers is an analog audio output or the built-in speakers on a laptop.

Digital Audio produces no sound,

Exactly what what are you connecting to the digital audio output and are you using an S/PDIF cable for the connection?

 

On the laptop, I connect only to internal speakers, ear buds, or external speakers on a Bluetooth connection (Bluetooth adapter on an old sound system - NAD). And no, I'm not using an S/PDIF cable. I was just interested to know what it is and what it's used for. I'm assuming that if I wanted to use it, I would need speakers that accepted optical input. Is there a noticeable difference in quality, between optical and analog?

 

Is there a noticeable difference in quality, between optical and analog

There could be. Assuming you are using a high quality audio source, such as playing a commercially pressed music CD, the analog output of the laptop would be limited to frequency response, distortion, and noise characteristics of the laptop's audio hardware. On the other hand, the S/PDIF digital output would probably be identical to the digital data coming off the CD, with no loss of quality.

Playing an MP3 music file on the laptop with a nominal bit rate might probably sound about the same for a digital or analog feed to a decent set of powered speakers.

 

I tried the Optical Audio and I didn't notice the difference that I remember. That was a long time ago with the PS3.

And to confirm, you do have this port on the right?

I haven't seen laptops with this port... I guess it's a high end specced machine?