Corroborating evidence (or corroboration) is evidence that supports a proposition already supported by initial evidence, therefore confirming the original proposition. For example, W, a witness, testifies that she saw X drive his automobile into a green car. Meanwhile, Y, another witness, testifies that when he examined X's car, later that day, he noticed green paint on its fender. There can also be corroborating evidence related to a certain source, such as what makes an author think a certain way due to the evidence that was supplied by witnesses or objects.
Another type of corroborating evidence comes from using the Baconian method, i.e. the method of agreement, method of difference, and method of concomitant variations.
These methods are followed in experimental design. They were codified by Francis Bacon, and developed further by John Stuart Mill and consist of controlling several variables, in turn, to establish which variables are causally connected. These principles are widely used intuitively in various kinds of proofs, demonstrations and investigations, in addition to being fundamental to experimental design.
In law, corroboration refers to the requirement in some jurisdictions, such as in Scotland, that any evidence adduced be backed up by at least one other source (see Corroboration in Scots law).
If one person says, “this is what I intended by the action I took,” and his friend agrees that his actions could have looked like what their friend intended. Then it can be generally agreed that is what happened.
If one person says, “this is what I meant by what I said,” and his friend agrees that was their understanding of what was meant by their friend. Then it can be generally agreed that is what was meant.
Think of this like backing up your mate in the playground no matter what they did or said.