CCK in Drupal 6 and FieldAPI in Drupal 7 give site builders a variety of structural and formatting options for carving out new content types. Multi-value fields in particular allow a node or other content element to store lists, collections of links to taxonomy terms, and more. The downside, of course, is the formatting: by default, Drupal's HTML output for multivalue text fields is a big old bag of DIVs. Taxonomy fare a bit better: they're output as proper HTML lists, a semantically proper approach. Both still require considerable CSS wrangling if you're interested in displaying multiple values simply, however. And that is where the Text Formatter module comes in.
Text Formatters was originally part of the much older "CCK Formatters" module. Its list formatting options were by far the most popular, and were split out into a separate module for ongoing maintenance. The module is stable, trouble-free, and does just what it promises. If you need to whip a few multi-value fields into shape, check it out!