Metainformation is information about information. For example, a if a document is considered to be information, its title, location, and subject are examples of metainformation. This term is sometimes used interchangably with the term metadata. The new field of knowledge management (KM) was developed to create systematic and reliable ways to manage data, information, and knowledge.
In a KM context, data, information, and knowledge are distinct from each other and have a hierarchical relationship. A collection of statistics is one example of data; information is any meaningful conclusions that can be drawn from the data (anything that informs). For example, the employment rates for every year (as long as they've been collected) are data. If we look at the numbers for last year and this year we have information, such as what the figures were for each year and how they compared. Knowledge, in this context, is a broader understanding that helps us to use the information to our best advantage, and might include, for example, factors that typically lead to a decrease in the employment rate.