This article explains what MetaDate is and how to use it.
What is MetaData?
Metadata is simply information about a file, article, or object. In the old network folders, the folder names themselves were the metadata as was the modified date or the creation date. In SharePoint, metadata is used to attach relevant information to a file, article or object.
In the example below, we can see the link to the "What is SharePoint" video. We know it is a video because one of the metadata columns gives us this information. This is great when you want to group sets of data together because you can tell the list to only show you links that are videos. You would do this by grouping or filtering your metadata.