Meaningful words attached to content and spaces.

Labels are words that you can attach to Confluence content to more easily identify, organize, and find/retrieve that content.

Labels can be attached to individual pieces of content (i.e., pages, blog posts, and attachments) as well as entire spaces.

For more information, please see 

Atlassian's documentation on using labels.

Users with Brikit Targeted Search installed have more options in how labels are presented, used, and organized.  Check out filters and filter groups to learn more.