Rig Types
Rig types are components used by Rigify to process specific parts of the meta-rig when generating the armature. They represent common character features, like the spine, limbs, fingers etc.
Opomba
The list of available rig types appears in the Bone properties tab when the bone is selected in Pose Mode. Scroll down the Properties to find Rigify Type panel.
This documents rig types that are bundled with Rigify.