Free Form Tagging
Taxonomy offers a hierarchical way to categorize your content, where tags offer a non-hierarchical way to categorize your content. You may use the Tags field while editing content to add a free form tag. This will help make your content more discoverable by the website's search engine.
For example, if you always refer to someone as "Bob" in your content but people search for "Robert" then you should add "Robert" to the page so that it is returned when users search the website.