difference between data and metadata

Metadata describes about data. It is ‘data about data’. It has information about how and when, by whom a certain data was collected and the data format. It is essential to understand information that is stored in data warehouses and xml-based web applications.

So, "meta" simply means "about the thing you're talking about". So metadata is data about the data. Data is information. Metadeta is information about the information. For example, you might have a chart that lists the population of each US State. You might then have details about that chart - what color it is, if it's a bar chart or a pie chart, what symbols are on it, etc. That would be metadata. 

Data dictionary is a file which consists of the basic definitions of a database. It contains the list of files that are available in the database, number of records in each file, and the information about the fields.

So,A data is individual facts, statistics, or items of information.Metadata describes other data. It provides information about a certain item's content. For example, an image may include metadata that describes how large the picture is, the color depth, the image resolution, when the image was created, and other data. A text document's metadata may contain information about how long the document is, who the author is, when the document was written, and a short summary of the document.