The footer is the lower part of a web structure that generally includes navigation links, links of interest, copyright or buttons to the social networks of the site.
The footer is usually clearly differentiated in some way from the rest of the website. Either by changing the background color of it or by changing the size of the typography.
This video will help illustrate everything:
Ideally, only the most important things should be included. We should not fill the footer with elements that do not contribute anything or confuse the user. Although it is a widespread practice, we should not include elements such as the site map, images or too much text.
As for the footer design, we can use colors that make it stand out but do not clash with the colors of the style guide. The footer is the central point in which to put the company's contact information so that the potential client has no excuse to contact you or to know a little more about your brand.