Two systems that look similar and do different jobs.
CATEGORIES
What the product fundamentally is. A product belongs in one or two categories.
TAGS
Cross-cutting descriptors: colour, occasion, material, style. A product may have several. Tags create their own archive pages, which can attract search traffic.
Do not duplicate your categories as tags. It creates two navigation systems that disagree.
ATTRIBUTES
Structured properties used for variations and filtering: Size, Colour, Capacity.
Create them globally under Products > Attributes, not on individual products. Only global attributes power filtering across the catalogue.
FILTERING
Attribute-based filters let customers narrow a category by size or colour. This is what makes a large catalogue usable, and it only works if attributes were set up globally and applied consistently.
PRACTICAL ADVICE
Decide your attribute list before adding products. Retrofitting attributes across three hundred products is slow work. Use consistent term names. "Blue", "blue" and "Navy Blue" become three separate filter options.
