SkinnedMesh
A mesh that has a Skeleton with bones that can then be used to animate the vertices of the geometry. The material must support skinning and have skinning enabled - see MeshStandardMaterial.skinning.
https://threejs.org/docs/#api/en/objects/SkinnedMesh
Joints Sometimes called bones, you can think of joints for rigging in the same way you think of joints in a human body. They basically work in the same way. Joints are the points of articulation you create to control the model. For instance, if you were to rig a character’s arm you would want to place a joint for the upper arm, another joint for the elbow and another joint for the wrist, which allows the animator to rotate the arm in a realistic way.
Skeletal animation is a technique in computer animation in which a character (or other articulated object) is represented in two parts: a surface representation used to draw the character (called skin or mesh ) and a hierarchical set of interconnected bones (called the skeleton or rig ) used to animate ( pose and keyframe ) the mesh. While this technique is often used to animate humans or more generally for organic modeling, it only serves to make the animation process more intuitive, and the same technique can be used to control the deformation of any object—such as a door, a spoon, a building, or a galaxy. When the animated object is more general than, for example, a humanoid character, the set of bones may not be hierarchical or interconnected, but it just represents a higher level description of the motion of the part of mesh or skin it is influencing.
YouTube
(unfortunately don’t know german, the examples look interesting)
In its simplest form, character rigging is the process of creating a skeleton for a 3D model so it can move. Character rigging is a very tedious process. It requires creativity, precision, and an eye for detail. As such, character riggers are responsible for using computer programs to form skeletons by creating a series of bones that deform and animate specific parts of the character.
Github
YouTube
@donmccurdy = 
his work with glTF
Workflow: Animation from Blender to three.js
Article
Github
New skinned mesh animation system in three.js r73 and r74
Article
Demo
References