Evidence comes in essentially two different Forms. What are these two Forms? Tangible and Intangible

Explain what they are in this example- A police officer who finds a gun [the murder weapon]at a murder scene. Two forms are represented here that would be necessary at trial.

my answer so far- The two forms that evidence comes in are Tangible and Intangible. In this example, the tangible evidence would be the gun/murder weapon. The intangible evidence would be what?