Footer
The most important things at a glance:
Definition: Lower section of a website with additional information and navigation
Purpose: Signals end of page, improves user experience & SEO
Mandatory information: Imprint, data protection, terms and conditions if applicable, revocation (especially for stores)
Optional content: Logo, payment methods, trust symbols, newsletter, social media links
SEO benefits: Internal linking for linkjuice, caution with external links
Technology: HTML tag <footer> for clear semantic structure
User behavior: Footer is deliberately accessed by interested users
Design tip: Clear, concise, recognizable - with repetition value for branding
Example website footer from DREIKON:

The importance for search engine optimization
In the past, the use of links in the footer was considered an effective measure for search engine optimization (SEO), as they could improve the ranking of a page. Nowadays, however, footer links are rarely used for external links. An exception could be the targeted use of footer links from the homepage, for example as recognition for the web design agency, in which case the link should preferably only contain the brand name instead of a generic keyword.
Website operators should generally be careful with external links from the footer. However, footer links can still be useful for internal links in order to direct the so-called link juice from the homepage to subpages. However, webmasters must be aware that this type of internal linking does not improve user-friendliness, but mainly serves search engine optimization strategies. With the ongoing developments in crawling technologies, it remains to be seen whether this practice of internal linking will continue to be necessary.
Conclusion
To summarize, the footer is an indispensable part of every website. It is located at the bottom of every page and contributes significantly to the user experience and the design of the website by providing additional information and help with navigation.
The footer fulfills several functions: It signals the end of the page, provides space for important information such as the imprint and privacy policy and enables internal linking for better distribution of link power. It can also be useful for search engine crawlers, which can navigate through the page more efficiently via deep links.