api guide link: https://guides.spreecommerce.com/api/
useful link: https://guides.spreecommerce.com/user/configuring_taxonomies.html
Taxonomies are the Spree system’s approach to category trees. The heading of a tree is called a Taxonomy. Any child branches are called Taxons. Taxons themselves can have their own branches.
Taxonomy represents an entire tree, whereas Taxons are the nodes that make up that tree.