Add another button for UI field set in admin I feel like I must not have the correct terms when searching on this topic.  I am relatively new to Drupal.  What I need to create is a field set in admin which has an Add Another Foo button so any given node could have as many Foo field sets as desired.  These would be draggable to sort for the node and accessible for the public facing twig to display.

Can someone help me with the terminology for this and if there is a tutorial on implementing I would really appreciate a link!

Example gui:
You're looking for the Paragraphs module. 

You can use it to create a paragraph type with the required fields in it (reference, specification, etc), than add a multi-valued field to your node type referencing that paragraph type. 

Because it's a field, you'll get the standard add another and sorting functionality.

The How to start with Paragraphs for Drupal 8 docs page should get you going pretty quickly.