The word data is the plural of datum, meaning a piece of information, or, "the given". It is also commonly used as a mass noun, where it is treated as singular, e.g., "This is all the data from the experiment". Many consider this usage incorrect, or at least colloquial, and would prefer "These are all the data from the experiment" (each individual measurement or result from the experiment is a single datum). The word datum is taking on a life of its own, however, and it is now most often used to mean a designated base point against which measurements are taken.
Raw data are numbers, characters, images, or other method of recording, Computers nearly always represent data in binary. in a form which can be assessed by a human or (especially) input into a computer, stored and processed there, or transmitted on some digital channel. Data on its own has no meaning, only when interpreted by some kind of data processing system does it take on meaning and become information.
People or computers can find patterns in data to perceive information, and information can be used to enhance knowledge. Since knowledge is prerequisite to wisdom, we always want more data and information. But, as modern societies verge on information overload, we especially need better ways to find patterns.
see also data processing, data mining, Data Warehouse, datasheet, Computer program