If the term set is open, then users can add new terms to the term set if the column is also configured to allow fill-in choices.Select the check box to make the terms in the term set available for tagging.However, if you want a Managed Metadata column to be reusable and broadly useful for others who may be creating new site content types or configuring lists and libraries, then you might want to create it as a site column.How and where you create Managed Metadata columns should be factored into your organization-wide planning for managed metadata, content types, document management, and site governance.You must have the Manage Lists permission level to create columns for lists or libraries. Specify whether you want the term set to be Closed or Open.If a term set is closed, then users cannot add new terms to it when they are updating the value for a Managed Metadata column bound to this term set, and the term set can be updated only by individuals with permission to update managed metadata.Because this term set is updated and managed separately from the column itself, there is no need to update the column (or any content types, lists, or libraries associated with it) to make updated terms available to users.Whenever the term set that a specific Managed Metadata column is bound to is updated, the updated terms will automatically become available to users wherever that Managed Metadata column is available.
The name of the term set and the term's position in the hierarchy can be indicated along with the term itself, which can help users select the appropriate term.
If you map the column to an individual term within a term set, then the column will display that term, and any terms underneath it in the hierarchy.
You can create a Managed Metadata column that maps to an existing term set or term at any level on a site (for example, as a site column, or as a column local to a specific list or library).
Managed Metadata columns promote the consistent use of metadata across sites because they provide users with a list of terms that they can apply to their content.
These terms come from a term set that is managed centrally in the Term Store Management Tool by a Term Store Administrator or other individuals with permissions to manage terms.