Corroborating evidence is supplementary evidence that tends to strengthen or confirm the initial evidence in court.
Corroborating evidence is important where the facts of a case are disputed by two or more witnesses. The side that can show their version of events is supported by other facts, will go a long way towards convincing a judge or jury that their version is more likely to be true.
For example: Bob is alleged to have punched Richard, but Bob denies this. Evidence that Bob later attended hospital with a damage to his wrist would tend to corroborate the fact the punch happened. On the other hand, evidence that a few days later Bob was Best Man at Richards Wedding would tend to corroborate that Richard is lying about being punched.