There are different types of evidence that are categorized by form or source. Testimony is one such type of evidence and come in written or oral form. The written form is called and affidavit and is a written and signed explanation from a person and is often used in business or civil law. There is also an oral form of testimony which is commonly seen on television coverage of court cases or in criminal dramas.
Evidence also may be presented as an exhibit which may be a physical object that is presented as evidence. Again, this is a common type of evidence seen on television.
Documentary evidence is any evidence presented as a document of the crime that occurred. This includes writings such as a contract or will, but includes any media that records and stores information, such as a video or voice recording or a photograph.
Another major type of evidence is demonstrative evidence. This type of evidence is a photograph, x-ray, autopsy or a reenactment of an action or event. It must portray an acurate description, but it is meant to help more clearly demonstrate other evidence that cannot be seen otherwise.