Inbetweens and Splining?

[Superior]

These three steps for animation are mentioned quite a bit and I would love to learn them, but my only problem is how? I have watched all the animation tuts for pose to pose, they helped quite a bit but it's not what I'm looking for. I love the graph editor and it's really all I want to use (unless something needs fixing, thats when I use the motion editor.) SFM's tuts are pretty much all done in the motion editor, something I don't like to use for animation. I usually animate by pressing spacebar, moving the model, then doing it again etc. I believe since I animate like that (and been doing it for a few years now it probably the reason why I get confused with Inbetweens, and Splining. Now, I do animate with splined tangents, but the term splining for this type of animation style seems to refer to something completely different. Splining for example, do I just grab all the keyframes and push the spline tangent? If so, why would I need to block in the first place?
Inbetweens, I can't pose inbetweens because I don't know how I'm going to pose the model to make it fit in with the other keyframes. This concept seems rather useful but more time consuming, which is something I am willing to risk to improve the overall quality of my animations. If ANY of you have any help, please try to get into as much detail as you can. Thanks!