Tags are a way to organize and relate articles with your knowledge base. Tags are different than keywords – you do not need to add tags to your articles for them to be returned in search results. By default, all the words in your article, including both the title and body as well as PDFs, are indexed for search.
Tags add a piece of metadata to an article, telling you or the reader more about what type of article it is or what the topic is. By default, tags are displayed in search results and readers can click on them to view all articles with the same tag. For example, you might have a tag called "troubleshooting" which tells you and the reader than this article is about troubleshooting and that there are probably other articles which are about troubleshooting as well.
You can search for all articles with the same tag by inputting a colon followed by the tag name. For example, putting ":troubleshooting" into search would return all articles with the tag "troubleshooting".
Tags do influence search results, and tags results are displayed below any exact match or search phrase results. For example, a search for "troubleshooting" would return articles tagged "troubleshooting" after any articles containing the word or search phrase (those would be exact matches).