A business glossary makes it possible to define fields used within an enterprise. It is a trusted reference business “dictionary” in an organization.
The Glossary's main objectives, among others, are to:
Use the same definitions and create a common language between all employees
Have better understanding and collaboration between business and IT teams
Associate business terms to other assets in the enterprise and offer an overview of their different connections
Elaborate and share a set of rules regarding data governance
Custom Fields allow you to create customized metrics to be used in your data transformations. Some reasons why you might create a Custom Term:
You use a calculated metric in your reporting that isn't available in the underlying dataset
You want to re-name a Standard Event with an easier to use alias (ie. Checkouts Initiated renamed to "Showtime Lookup"
You want to use Data Blending and create your own cross Dataset dimensions
Your Company Glossary will capture and store all the fields across all Workspaces. Company admins will have access to the Company Glossary.
Permissions and access is managed via Workspaces, this allows company admins to share specific fields into a workspace and trust that the collaborators in that Workspace will only have access to the data they need.