anything presented in support of an assertion
Evidence is something that is used to support an argument. It gives examples of why something is true.
For example, if someone come across a cup of spilled milk, that person could look for evidence as to how the milk was spilled. If hairs of a cat and paw prints were found on the ground, they could be evidence that a cat was the cause of the spilled milk. If a witness saw the cat spilling the milk, her testimony would also be evidence.