Corroboration is evidence or proof that a belief, theory, or idea is accurate. A corroboration helps prove something by providing additional support. Corroborating evidence is something that supports a previous theory or belief.
For example, crime investigators have a suspect for a robbery in custody because of an eyewitness. But they need corroborating evidence in order to ensure they have the person who committed the crime. Corroborations would include fingerprints or DNA evidence at the scene of the robbery or other eye witnesses. These are supporting evidence that the suspect did indeed commit the crime.