In general terms, data are raw, unorganised facts. They can be categorised under various types, including numeric, text, date/time, alphanumeric, logical, graphics, audio and video.

Data can be obtained in a number of ways from either primary or secondary sources. Primary data are facts obtained first-hand, usually through interviews, questionnaires and surveys. Secondary data are facts collected or created by someone else. Secondary data can be gathered from both print media and electronic media. When data is obtained from any secondary source it must be correctly cited.

In order for data to be useful to anyone, it needs to be reliable. Reliable data is data that is accurate, error free, presented in a suitable format, is obtained at a suitable time and is free from bias.

Data can be split into two categories: Quantative data and qualative data. Quantative data can be expressed in the form of numbers, such as test results, counts and yes/no responses, whereas qualative data is not easily expressed in numbers. Some examples of qualative data includes histories, anecdotes and descriptive interview responses.