Similarly to "header" element, "footer" element is often referred to the footer of a web page. Well, most of the time, footer can be used as what we thought.
A footer typically contains information about its section such as who wrote it, links to related documents, copyright data, and the like.
Please don't think you can only have one footer per web document, you can have a footer in every section, or every article.
Please see the example below, there two article elements are footed by footer elements and there is a site wide footer element which serves a main footer of the web document.