Switching gears from my usual metadata topics to Search Engine Optimization. I found a great series of courses related to using meta tags for SEO over on SEO Hacker.
Meta tags are the words that are hidden in your code, in the HTML <head> area. This is where you can put titles, descriptions and keywords that help crawlers locate your content.
There are three main things that a search engine crawler does with your meta tags. These are used for indexing, retrieval and ranking or precision.
Primarily, SEO experts use meta tags for things like accounting for misspellings, adding synonyms and also describing web pages with visual not text elements.
Read the whole thing to fully understand meta tags, proper use in SEO and the purpose of meta robots.