Meta-data represents the information about web-page content.
This information is used by search systems and search bots during the indexation. After that, the meta-data of the page is used when the lists with search results are generated for users.
Meta-data include lots of information but the most important for the website page are the title, the header, the description, key words, etc. They are basically not displayed on the website page except the header and the title. The header is represented sometimes on the website page, while the title is displayed in the top of the tab in the browser window.