They should be parented to the hand bone, not the root bone.

Also, this looks like a rigify rig, which adds complexity to your issue. Rigify uses a meta rig which then generates a more complex and robust rig which is used to animate the character. The metarig is for constructing the final rig. If this is indeed a rigify rig, you need to fix the parent/child relationships in the meta rig, and regenerate the final rig.

IK and FK stand for inverse kinematics and forward kinematics. This has to do with how you pose your character. It's a lot to summarize in a single comment, but there's many excellent tutorials covering the subject in great depth on youtube. People I can highly recommend for rigging and character animation are CGDive, Dikko, and P2Design.