Explicit knowledge is knowledge that has been articulated, codified, and stored in certain media. It can be readily transmitted to others. The information contained in encyclopedias (including Wikipedia) are good examples of explicit knowledge.
The most common forms of explicit knowledge are manuals, documents, procedures, and how-to videos. Knowledge also can be audio-visual. Works of art and product design can be seen as other forms of explicit knowledge where human skills, motives and knowledge are externalized.
See also 
- National Library for Health Knowledge Management Specialist Library - collection of resources about auditing intellectual capital.