Tacit knowledge (as opposed to formal, codified or explicit knowledge) is the kind of knowledge that is difficult to transfer to another person by means of writing it down or verbalizing it. For example, that London is in the United Kingdom is a piece of explicit knowledge that can be written down, transmitted, and understood by a recipient. However, the ability to speak a language, knead dough, play a musical instrument, or design and use complex equipment requires all sorts of knowledge that is not always known explicitly, even by expert practitioners, and which is difficult or impossible to explicitly transfer to other people.
How much of working in an IT environment is tacitly learned? How much of that can be made explicit?
UI Development – How should a new item look? It should fit in. What does that mean? You should just know. What’s appropriate on a site for insurance companies vs what is appropriate for a site for surfing gear? Same thing, you should know by experience.
A common one – learning how the existing software works is often tacit. You get a ticket to modify some existing functionality. How it currently works, how it’s supposed to work, how to run it, what problems are known vs what problems are new. How often is all that directly explained?