The difference between motion capture (mocap) and performance capture (Pcap) is the extra detail—especially in facial expressions—that Pcap records.
Motion capture records the major body movements of an actor or stunt performer through mocap suits or special camera techniques. That data is transferred to a rigged 3D character model.
In addition to body movements, Pcap also captures an actor’s much more data-dense facial expressions and subtle gestures. This is accomplished through marker tracking on the actor’s face and body or through newer 3D scanning methods that translate every frame of a camera recording into performance data that can be transferred onto 3D character models—resulting in highly realistic and genuine CGI performances.