Like a classic HTML sitemap, a footer sitemap is intended to both human visitors and search engine spiders. As the name suggests, footer sitemaps are placed in a footer webpage and most often on almost every page of a website.
As they are in the footer far below the fold, they are rarely seen by visitors and it may be inferred that their main purpose is search engine optimization by creation of internal links. For more details about footer sitemap goals, see HTML sitemap definition.
Footer sitemap are usually lighter than stand alone HTML sitemaps. On large ecommerce website they tend to only point to additional informations and services and sometimes big product categories.
A footer sitemap can also be sometimes used in emails for navigation purposes
Some footer sitemap examples :