In this article we can explore Open and Closed Term Sets inside SharePoint.
Term Sets allow users to create collection of terms which they can reuse to associate with content.
Usually the Site Owner creates the Term Sets for all the other users.
Example of a Term Set is Programming Languages with values like:
Term Store Management Tool
For site collections we can use the Term Store Management Tool. This is available from Site Actions > Site Settings > Term store management tool
Closed Term Sets
By default Term Sets are closed. Here the term manager has to create the terms & users will have to use it. There is no provision to add new terms on the fly.
Term association dialog is shown below.
Open Term Sets
Open Term Sets allows users to create more terms on the fly.
Once we mark the same Term Set as Open, we can add new terms in the association time.
Selecting a parent term & clicking Add New Item allows us to create new term under the parent.
Groups, Term Sets & Terms
Please note that there is subtle difference between Groups, Term Sets & Terms. You can notice the icons for the same.
In this article we have explored Open and Closed Term sets.