Normal Bones vs Bendy Bones

Hi, im a newbie with the rigging and i want to learn more about this.

My question is, doing the skinny with automatic weights. What type of bone its more useful?
Normal Bone or Bendy Bone.
I don’t know the difference between both.

If someone could explain me the difference or bring me some source to learn more about this topic i would be very gratefully.

Thanks you.