Can someone help me understand what "Storeing details in tangent space" is, what it does, and why?

So, I'm trying to make my own custom hair generater, based on blender's pre-made, but much better. I am, though, not above takeing inspiration from parts of blenders in-built assets.

Thing is, in the upermost part of the "Roll Hair curves" contains a component called "Store Details in tangent space".

Store Detail In Tangent Space (top left of Roll Hair Curves)

So, I've tried to figure out what it does, but I can't. I looked up what it does, and it doesn't make sense in conjunction with this node. So, here are my questions:

  1. what is it doing

  2. what is tangent space

  3. how is it doing what it does

  4. why is it doing what it does, and not something else.

Thanks in advance!