The MS addition to the RG name means that the guitar is equipped with a multi-scale neck (often called Fanned Frets), which can look a little crazy to someone who has never seen it before.
Multi Scale is what it sounds like, simply that each string has a different scale/scaling, longer on the low/thick strings and shorter on the high/thin ones.
Ibanez were the first to build Multi Scale, Fanned Frets, or whatever you want to call this amazing invention, on instruments that are not custom-made boutique instruments (but a price tag afterwards). All to find satisfactory solutions to the problems that modern metal musicians encounter with low-tuned guitars. That is, the low strings become fluttery and unclear if the ''solo strings'' should feel playable. Or conversely, if the low strings are good, they become bright, almost unplayable fingerpicks. To get stability in the low range, you either need a longer scale or very thick strings, often a combination of both.
With multiscale, you get an instrument that feels and plays perfectly balanced across the entire register, the ultimate compromise between two conflicting goals.
