SharePoint Short #12
Instead of creating term sets that are available farm wide, it’s also possible to create a term set that is only local to a particular site collection.
Create a site column as normal, selecting Managed Metadata type
Within the Term Set Settings section, select Customize your term set:
Then simply add terms to the top level node (same name as your column by default) and once your happy click OK to create your metadata column based on a local term set.