Metadata communicates primarily to web browser software and search engine robots. Metadata is applied to a web document inside of its <head> element by using the <meta> element to specify the meta information you wish to relate. Applying meta tags or metadata will not get you a top spot in search engines, that determination is made by a combination of many factors outside the realm of this discussion.
I will place more metadata examples(there are a stunning amout of meta "name" types you can apply) as I get time to, but this is a fine start for you covering popular usage of metadata communication to browser software and search engine robots.
Refresh the web document every 3 minutes
This sets a refresh setting to let the browser software know how many seconds to wait, then refresh the document.
Title for Web Page
While it is not an actual meta tag, the HTML title tag relates important meta information.
Character Setting for web page
Attribute of the meta tag for relating the character encoding of the web page.
Description for web page
A few sentences describing the web page content. This metadata has significance to all search engines and autonomous data grabbing software.
Keywords for web page
Keywords are key phrases and words that relate to the page content. Many search engines still use this metadata for search relevance and result placement, as well as autonomous software. Google search bots stopped using the keywords metadata for relevance due to the way a web page author could manipulate the data in it to trick crawlers into thinking their page contained certain content, while the author serves up content that has nothing to do with the keywords they applied.
Robot content spidering
You can choose to allow or block robots using this metadata. Using "all" allows all robots to index the content. You can also block specific robots while allowing others.
Instructs autonomous software to return and re-spider your content after a time interval.
Author of Page Content
Specify the author of the content on the page.