A silo is a section of a website focused on a particular "searcher intent", theme, or keyword phrase. Not just a page that mentions these things, but a focused section of a website. A silo should be built for each of the different themes a website is covering, with a main page about each subject, focused on each of these subjects. The main navigation of the website should link directly to these pages, and then there should be links from those pages to any needed sub-pages. Silos are a a method of focusing the link juice into specific areas of a website for specific keyword phrases. Silos demonstrate the E-A-T of a website for a specific term or theme. Silos are also known as "pillar pages" which lead to sub-pages ("cluster pages") focused on sub-pieces of that subject. An example is a website for a company that does "air duct cleaning" and "industrial cleaning". It would link from the main menu to an "air duct cleaning" page, which might link to a page about methods, a page about tools, a page about the process of cleaning an air duct, etc.
