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.
For example, you can use Jekyll to first convert your blog content into static resources. Afterwards, Jekyll simply reply HTTP clients with these resources without any modification.