A Subject-Matter Expert is someone who is an expert in a particular topic or profession and offers their knowledge to a company, community or variety of clients.
Subject-matter experts are seen as authority figures within their field thanks to their in-depth knowledge and, crucially, their experience. By working with a subject-matter expert, an organisation can learn how to develop their own strategies based on a better understanding of the industry.
These experts are often employed to give speeches at seminars and other similar events, although many larger corporations higher them internally to train people entering high-ranking positions.