Cartridge/Tonearm matching fundamentals?

TWL made a comment on a recent thread about two very nice cartridges (Shelter 501 and Lyra Lydian Beta) not being suitable for a unipivot tonearm like the JMW.

I know nothing about the concepts of matching cartridges and tonearms (nor much about tonearm types) and was wondering if TWL (or a similarly knowledgeable soul) could share some of the basics on the topic with the unenlightened.

I don't understand either the term "higher compliance range", not the different tonearm types (unipivot vs. ?) and thus why, in the thread in question, neither the 501 nor the Beta won't work on a particular tonearm.

As a point of reference, I recently acquired a VPI HW19 MKII with RB600, have purchased but not received a Dynavector 20XH.

Thanks in advance,

Tim Wat