As an additional note: can you just use the DEF bones to animate? Yes. However it will make animating more difficult and time consuming. Take a simple thing like stepping forward. Just a step, not a full walk cycle. Every time you make an adjustment to the bend of the knee you have to then move the upper leg so the foot is still on the ground. When you pull the body down you have to adjust the legs and foot to keep the foot from going through the ground. This is called counter animating. This is why IK is such a game changer. You plant the foot on the ground or up in the air and then when you move the hips down the leg automatically bends and adjust to keep the foot where it’s at.
