Experience is knowledge of and skill in something gained through being involved in it or exposed to it over a period of time. It generally refers to know-how or procedural knowledge, rather than propositional knowledge. Knowledge based on experience is also known as empirical knowledge or a posteriori knowledge. A person with considerable experience in a certain field is called an expert.
If someone is recounting an event they witnessed or took part off they are said to have had a "First hand experience".