Ortofon tonearms ,Static and Dynamic - Difference?

I see there are 4 new Ortofon tonearms.

Static tone arms: AS-212-S and AS-309-S
Dynamic tone arms: RS-212-D and RS-309-D

http://www.merrillaudio.com/tonearmscarts.html

What are the differences sonically and in general use of the Static and Dynamic versions of each??