Predefined tags allow administrator to specify a predefined list of words that community members can tag an idea with. Customize your list of tags in general tag list.
Path: Community Settings >>Customization >>Tag Settings >> Predefined Tags.
1) Predefined Tags : The Administrator may want the community members to tag ideas, choosing from the valid list of words he has predefined as tags . When Predefined tags are enabled the users have the ability to only select a tag-word from the existing list .
2) Hybrid Tags : The Administrator predefines the tag words for the members but at times the member may not be able find an appropriate word to tag his idea in the list of predefined tags and may want add a new tag-word to the existing list of tags. Hybrid Tags allows this flexibility.
Help Article: http://support.ideascale.com/customer/portal/articles/1923170-bulk-import-tags