To learn how Digital Audio Workstations work, you’ve got to get hands-on.
If you don’t have a DAW yourself yet, then watching someone else get hands-on is your best bet. There’s a huge number of online tutorials available for all the major DAW programs, way more than could be listed here comfortably. To get you started, here are three videos that provide a basic introduction to three of the most popular DAWs. This first clip gives a quick rundown on recording with the LE version of Pro Tools 8 (LE stands for Light Edition, as opposed to the more expensive Professional Edition), using a combination of software instruments and real ones.
In this clip, you can see how a beat gets created in Ableton Live 9. No real instruments this time; we’re entirely in software world here.
Continuing with the software-only approach, this is an introduction to Logic Pro X.
Again, the number of tutorial videos for both the DAWs above and many others is large, so if what you see here interests you, plan on exploring further. There’s no better way to decide which DAW you like best than by seeing how they all do what they do.