And what's IK, and what was the other one, FK?
TL;DRIK (inverse kinematics) lets an animator drag the end of a joint chain, while FK means rotating each joint one at a time, which makes IK much easier for 3D animation.
IK stands for inverse kinematics and I can show you real simply what that is all about. So FK. So to get FK to work, I'm going to have to rotate my arm up. Let's say he's going to point at something. Then I got to go select my elbow and I got to bend at the elbow and then I got to select the hand and get the hand into position. And that's how I'd have to animate the entire character. And then one day somebody got the idea of being able to create an inverse kinematic chain. And what that does is it allows me to grab the end of a chain of joints and drag it around, making it much, much easier to kind of drag and rotate and point or grab onto something. And I'm old enough to remember what it was like pre-IK. And IK has made animation in 3D so much easier. So much nicer.