There are hundreds of different ways to store data on a computer and each one is a separate data format. The reason there are so many different data formats is because each type of data has a different way to store it that is most effective. The efficiency of a data storage format is usually measured by the the amount of space the data object consumes in that format, and the speed at which the data object can be stored to, or retrieved from, the format. Usually it is not possible to optimize a format for both speed and size and therefore trade-offs have to be made between the two.

For example, the JPEG (Joint Photographic Experts Group) file format is excellent for storing pictures but not suitable for storing text documents. It can be used for storing pictures of a text document, but the resulting file size will be much larger than that of a simple text file. In the case of storing a document a standard text file format will be much more efficient than the JPEG file format. However, standard simple text file formats can't store pictures.