Novice Question: Dedicated Streamers

@ahofer laid it out really well.  I like to think of these in a few buckets:

-  DAC with streamer functionality, has digital+network in, digital+analog out  (Auralic, MSB, NAD, others)
-  Streamer with DAC functionality, has network in, digital+analog out (Lumin, others)
-  Streamers, has network in and digital out, needs external DAC (Lumin, Auralic, Sonore, others)
-  Network Music Server and Streamer, has digital out (Aurender, others)
- Network Music Server, Streamer, and DAC (Aurender, others)

There are also computer based network severs which can have DACS.  These usually have specialized hardware, like linear power supplies, around computer parts (Innuos, Roon).

Also there is just software solutions that can be installed on your computer at home which can act as a server. (Roon, others)

The theory behind this is is that the more specialized the component the better the sound.  Each will have a different interface and mobile app to go with it.  Some share compatible with Roon, mostly as an endpoint.

This isn’t all inclusive of all solutions, but hope it helps.

If you're streaming music through your MAC or computer, you don't really need a streamer. 

If you have a dedicated 2 channel system that doesn't have a computer the streamer provides the functionality you get from the computer - internet connectivity to download/stream files, an interface to select music (often through your phone or tablet), and the firmware/hardware to decode the digital signal and send it to your preamp/amp.  It's basically another source, like a CD player, turntable, etc.

You may find that a dedicated streaming device provides better sound quality than your computer.

I gave up on hard media like vinyl and CD’s years ago and was an early adopter for computer audio. I only stream music through a dedicated streamer-dac box using a music subscription service. BTW, I uploaded my entire CD collection into a solid state drive that I plug into the streamer and access that music if I’m in the mood. So for me the convenience and very easy access to a broad music library is key for me. BTW, the sound quality is terrific IMO, with my gear. However, if you like CD and/or vinyl and the "work" it entails, that’s fine too.

This all clears up a lot for me.  Thanks, all!  Prob. For the foreseeable future, I’ll continue to stream tunes from my Mac > Airport Express....I’d eventually like to acquire a better DAC and go wired rather than wireless (rare dropouts but they do happen when the microwave oven is running!).  It all sounds pretty wonderful now, as is but...well...upgrade-itis lol.

I think the OP query has been answered, I’ll just chime in with reiterating that streamers and PC based streaming are essentially similar.  Streamers remove the PC from the equation, but are in themselves computers with specialized OS.  There are are many theoretical advantages to removing the PC and using dedicated audio components.  Having done both, they both can deliver great sound.  Personally, since I stare at a computer screen all day at work, I don’t wish to be dealing with one while relaxing with music at home, but ymmv