A static website is a collection of resources that is served by HTTP servers without any modifications.
Because no modification is made to the resources, it can be faster to access a static website as compared to a dynamic website.
Usually, a static website is made for promotional content that are short-lived. For example, the perks for using a credit card on a particular month can be presented with a static website. Another example can be an online resume of a fresh graduate.
It is also possible to present dynamic content as a static website. In order to do so, you can create a procedure to convert your content into static resources. Afterwards, you can setup a HTTP server to serve those resources statically.