You’ll need to be more specific, maybe circle the part in the image you are talking about.
Assuming you mean the top image, with the outside of the grip and not the broken down inside view, yeah that’s almost certainly a bumpmap. Assuming that the inset section on the grip is not a separate object (which it absolutely could be, we can’t tell without a wireframe view or an object ID render), it probably would be by carefully building the topology of the handgrip as a whole. And then, where the padded inset is, you would want to cut in the outline of the inset into the existing polys and build the proper edgeflow/polyloops. And once you have that initial cut set up, you will usually add at least 2 more holding edges for that sharp transition/inset, or possibly a little less holding edges but with a crease set on the right edges to build that hard edge.