Keys for controlling bones in Pose Mode

While I’m not completely new to Blender, I’ve noticed that the G key does essentially the same thing as the R key - they rotate the bones when trying to pose them in Pose Mode. I’m pretty sure that I’ve seen people that, when using the G key, the bone’s “tail” end will track to the movement of the mouse, also allowing control over other parent bones. Does this happen when an armature is set up in a certain way, or is there an option to allow this?

the easiest way to do this is to toggle ‘auto IK’. another way is to set up an IK solver constraint.
(edit) IK stands for inverse kinematics as opposed to forward kinematics, which is the way bones work by default

Where is the location for the “Auto IK”? I seem to be missing it.

it’ll be on the left in the tool shelf while you’re in pose mode

Thanks so much! Works perfectly.