Labels assigned to knowledge base articles or tickets enable you to find related articles or tickets.
You can define multiple labels to filter for in the Knowledge Base. To do so, on the
page, search for a label. Then perform another search for the next label, and so on. Only those articles will be listed that have all labels applied.You can remove filters one by one by clicking Clear next to the unnecessary filter.
See also How do I assign a label to a ticket?