Meta data is "data about data." Example: the label on a file folder, telling you what the folder contains, is one type of "meta data". The meta data about a web page is placed into meta tags in the code of the page; those meta tags contain information about that page, such as the title of the page and a description of the page suitable for humans to understand.
Celebrating 25 Years of Creating an Island of Stability In the Sea of Online Confusion