Knowledge is usually defined as awareness of/or familiarity with facts and as practical skills. The first type of knowledge is often referred to as knowing that in the sense of knowing that something is the case; the second as knowing how in the sense of knowing how to do or make something.

Both forms of knowledge are produced through observation; information gathered through the human senses and/or sensing technologies; research and comparison of axioms, opinions, and theories; experimentation; measurement and calculation; and contemplation or introspection.