Evidence is a fact or information that is used to support or prove an idea or claim.
Evidence does not speak for itself, but must be interpreted. For example, a judge or jury must decide whether a gun found at the scene of a crime (the evidence) supports the prosecutor's claim that the gun's owner was present, or whether the gun got there by other means.
Evidence must be able to distinguish between two competing claims. For example, similarity of living things (homology) does not necessarily support the theory of evolution over the creationary viewpoint because the same evidence is consistent with both ideas.