Metadate means 'data about data'. When a file is saved, information about the file is saved with it. This could include:
This type of metadata can make it easier to find a particular file if you have forgotten the name of it, but can remember approximately when you created it.
Metadata about a digital image will also include:
From this information, the computer can interpret the binary digits to recreate the image on screen or paper.
Example of a metadata display showing the key properties of an image.