Managed terms and enterprise keywords are stored in a database known as a term store
Managed metadata is a hierarchical collection of centrally managed terms that you can define, and then use as attributes for items in SharePoint Server.
- Managed terms, which are usually pre-defined, can only be created by users who have the appropriate permissions, and are often organized into a hierarchy.
- Enterprise keywords, which are merely words or phrases that were added to SharePoint items. All enterprise keywords are part of a single, non-hierarchical term set that is named the keyword set.
Both managed terms and enterprise keywords are stored in a database known as a term store.
Reference: Overview of managed metadata in SharePoint Server 2013
