Global attributes allow a store admin to add particular product properties store-wide. Hence global attributes can be used to assign some common properties to all products in your store. Unlike product-specific and product class attributes, global attributes allow a store admin to assign hidden attributes to products that can be used for internal store management purposes and visible only to the store admin.
Global attributes can either be added manually on a per-product basis or imported and assigned to multiple or all products in the store at once.
Generally, global attributes are viewed and managed via the Classes & Attributes section of the Admin area (Catalog -> Classes & Attributes).
The global attributes listing page:
However, if necessary, it’s also possible to create and manage global attributes (except hidden global attributes) via the Attributes -> Global tab of any product details page.