META tag, not MEAT tag It's ON-page. Go read up about meta elements on Wikipiedia http://en.wikipedia.org/wiki/Meta_element
Meta tag is used for on page work. Meta tags can also help improve placement (or ranking) of your web pages in search engines like google.
META tag is on-page and there are 4 parts to it, you have (1) Page Title Tags Generations (2) META description and marketing tags (3) Geographical target market tags (4) Main content suggestions.
Meta tag is an on page process. Sometimes when a user searches a query Google will take the description as a snippet If it is more relevant. Refer webmasters you tube video to know more about how google use meta description.