It's the famous flat speaker (think of most modern speakers) vs a "live" speaker (klipsch, zu, etc).
To me, a flat speaker blends everything together, as if it's all on the same playing field. Level. Flat. And many think, boring. I would agree.
A "live" speaker sounds more layered. A drum cymbal leaves that "flat" space and sounds dynamic. Anything that deserves an "attack" gets an attack.
That's what they mean by "live". Live isn't perfect or accurate. Just like every single live show I've been too...nothing is perfect as it's not intending to replicate the studio.
Instruments are more spatial in nature and are very forward facing. It's a more aggressive speaker type.
That's my non-audiophile explanation.