The Armature Object in itself is a tool for the animator to move an object or group of vertices in a reliable way. An armature is made of bones, which can be parented to each other, or connected to each other. It was built with the idea of a skeleton in mind. And in fact, in the 3D world with animation inclusive, its considered to be the skeleton.
You can add it using the SPACEKEY in 3Dview and selecting Armature. You'll then enter into Edit Mode where you can add or move bones to build your default rig. An armature has 3 states. You can switch using the dropdown menu in the header of the 3Dview or use the TABKEY to switch between Editmode <-> [Objectmode|Posemode] and CTRL-TABKEY to switch between Objectmode <-->Posemode:
- Object Mode: Your armature is like any other Object, you can move it around the scene, scale it, rotate it and edit options in the button window.
- Edit Mode: Your armature is in what we call rest position, you can modify the bones it contains.
- Pose Mode: Your armature is ready to be animated, each bone can be moved, scaled or rotated, constraints get applied, you can pose your character and animate the bones' behavior over time.
Take note that Pose mode is now a state of the armature you can switch on/off using CTRL-TABKEY. So when in Pose, you are still in object mode (you can select another object, contrary to the edit-mode)
Note: The following 3 pages of this tutorial contain screenshots and discuss techniques that are only available in Blender 2.40a and later. Refer to the Blender 2.40a release notes on Armature draw types and Armature envelopes.