I think I’m quoting another BassChatter here when I say it seems to have a couple of meanings to different people but to me (and do excus e my not very technical lay-person’s explanation here) it is about traditional bass amps and cabs having a very ‘coloured’ output, so you might want a truer idea of what your instrument really sounds like without the ‘colour’. Some powered PA speakers give such a ‘colourless’ sound, if not completely ‘colourless’ then close, certainly closer than a traditional amp/cab setup. Also, once you start exploring this avenue you might (or might not) be persuaded that actually such a powered PA speaker might be able to completely replace an amp/cab rig. I have done this recently and I’m not going back. Like @Bridgehouse, I now play my bass through a preamp into a powered PA speaker and when I gig I send a DI from the PA speaker to the desk. The forty pages of discussion on the Interesting FRFR thread has radically changed my approach to amplification in all scenarios, a complete game changer for me.