Normal tags are about the content of the page, whereas meta tags are about the quality or characteristic of the content of the page.
Take a look at the children pages to see what meta tags are available. All of them have descriptions for when to use them.
In general, if you make a significant edit to a page, and feel that a meta tag no longer applies, feel free to delete it.
Meta tag pages should have aliases that end with "meta_tag", e.g. "too_long_meta_tag".