VOXEL is a visualized work credentials. In VESS, your work credentials is visualized as colorful 3D cube. If you want to know more about VOXEL, please visit below.
Sig. request is a signature request from who created VOXEL. VOXEL's trustworthiness gets higher if signatures of both of Tx sender and receiver are attached rather than a signature of one side are attached. So, when a VOXEL created by one side, a sig. request to the VOXEL is sent to the other side simultaneously.