False evidence means information or things that are shown as proof but are not true. It is like telling someone that you saw a talking dog when you really did not.
Think of it this way: If you want to prove that your chocolate cake is the best, you might say that 10 people tried it and loved it. But if you lie and say that 100 people tried it and loved it, that's false evidence.
People might use false evidence to try to make someone believe something that is not true. This is not good because it can cause harm to others and can create misunderstandings.
That's why it's important to always make sure that the evidence is true before we say something is the truth. And if we find out that someone used false evidence, we should tell them that it's not right to do so.