Data, Information & Knowledge.
Data = symbols. These symbols are without meaning. An example of this are the symbol of a number or a letter.
The Database is a group of symbols. An example is OPAC.
Information is when a symbol is compose of meaning. You get the meaning when you get a relation between symbols.
Knowledge is when you put in relationship all kind of information you have. Also is the selection of information you achieve from the research at a searching engine.
To sum up all this definitions, begining on data, once you have a relation with its meaning, you get some kind of information and when you put all them together you get knowledge.