Imagine you have a news web site with decades of news articles. You add a new article, which changes the "Top articles" section on a side bar. With a static g

Imagine you have a news web site with decades of news articles. You add a new article, which changes the "Top articles" section on a side bar. With a static generator, you would need to rebuild every single article, which may take minutes or even longer, using both CPU and disk I/O. With a dynamic generator, you might maintain a cache of the latest articles somewhere, and stitch it into another cached copy of the newspaper section chrome, and then insert the content. It might be more CPU in total, but the changes are live faster, and the total disk I/O would be much lower. Also, you'd need more disk space with a static generator. For most simple sites and blogs, there's no real resource use regenerating the entire site, so you get all the benefits of the static generator, and almost none of the drawbacks.