Generally it means they're simulating analog synth components in software; i.e. starting with oscillators producing stuff like triangle or sawtooth waveforms, running it through high pass and low pass filters and an amplitude envelope, throwing in some low-frequency oscillators controlling various parameters, adding some effects like reverb at the end.

That way you're doing the same stuff you would in a pure analog synth, and getting similar sounds. In the digital realm there are lots of other ways to make sounds: FM, additive, samples, physical modeling, etc.

Pure analog synth hardware had fallen out of favor by the turn of the century but since then it's made a comeback.

Thanks for the clarification.

I know that there is a semantic difference in technical contexts. It doesn’t bother me. It’s a true-enough Scotsman.

The distinction for me is with sampling synths (which can also, though rarely be analog)…I mean I have a forty plus year passing interest and the personality to gravitate to HN.

I am more interested in the empirical part. And digital has some practical advantages like using my iPhone.