Each bone has two joints. The joint at one end is the root, and the other is the tip. Joints control bones, and bones control objects (attachments).

Note: you can't select a bone in trueSpace by clicking on it.
To select a bone, select the joint at it's tip, or use the bone
list. If you select a bone in Motion Studio the joint at the tip
of the bone is selected in trueSpace. When you select a joint, the first bone
that has that joint as a tip is selected in Motion Studio.
You control the orientation of a bones by moving the joints,
but the rotation about the axis of the bone (twist) works differently.
Usually, twist is controlled automatically by the bone, but twist can be adjusted
manually using the green spin control in the Bone
panel. Twist is keyframed.
A bone has a root and a tip. All bones connected to the tip of this bone are it's child bones. Bones connected to the root of this bone are it's parent bones. Use the Flip button in the Bone panel to to change which end is the root and which is the tip.
See Parenting for more information about parent and child bones.