The essential thing to understand when it comes to skeletal animation is how bones and joints work together, as well as how to use them effectively in setting up a skeleton for a sprite or mesh.
You'll often hear people using either bones or joints, but they're not mutually exclusive. What is really meant is that when you actually define the components of a skeleton, you can define either the bones or the joints; the skeleton doesn't change, just the way you describe it. This means the following:
Defining the skeleton in terms of bones: Define the two ends of each bone and at least one connecting bone
Defining the skeleton in terms of joints: Define the location of each joint and at least one connecting joint
The advantage of defining joints instead of bones lies in the amount of memory you use. It follows naturally that a skeleton of multiple connected bones will have fewer joints than bones. For every two bones you define, you'd need to define only one joint. Whether the memory...