SSI stands for Server Side Includes. Server Side Includes allow web developers to include some limited dynamic content within static HTML pages.
An example of an SSI would be a ‘last updated’ field which automatically plugs in the date that the page was amended.
SSIs may also be used to create headers and footers which are applied to every page on a website. This enables you to easily make changes to the header and footer by editing a single file which is applied across every webpage.