The new anthro/anthropomorphic character, or in other words "R30" is a new avatar type in ROBLOX which resembles a human-like form for your ROBLOX avatar. This new ROBLOX mode was announced in the ROBLOX Developers Conference 2017.
In this new type of avatar, there are more humanoid features such as facial features, human-like arms and legs, hands, and etc, etc.
There are new avatar animations to this mode, which are quite similar to the original R15 animations, but adds a bit more of a human-like look.
These new characters appear to be a bit taller than the original ROBLOX avatar, although they might shrink them down to match ROBLOX's game physics, or they could've made the hitbox the same as the R15's and R6's, which may cause visual problems.