One thing is evidence for a second thing if the second thing is more probable given the first, than the second without considering the first. Thus the fact that you are reading this blog post is evidence that you are a native English speaker, since someone reading the post is more likely to be a native English speaker than a random person is.
One common mistake is to think that there cannot be evidence for something false; but my position is true and the opposite is false; therefore there cannot be any evidence against my position. Thus people say things like, “Evolutionary belief is a remarkable and largely unexplained phenomenon. It is a belief held by most intellectuals all over the world, despite the fact that there is no real scientific evidence for it at all.” Again, someone holding another position says, “Critics of evolution claim that it is just a theory for which there is no proof. It is true there is no definitive proof, and nor is there likely to be, but there is a vast amount of evidence in its favour. Whether you choose to believe it is sufficient is up to you, but it is there. By contrast, there is no scientific evidence for creationism.”
The claim that your opponent’s position has no evidence for it is always false, without exception. For the very fact that your opponent holds the position is evidence for it, since a position that someone holds is more likely to be true than a random position that no one holds. But even apart from this, given any particular position that real people hold, we can expect to be able to find any number of facts that make more it more likely than it would be without those facts, even if the thing is absolutely false. Thus if you buy a lottery ticket, it is evidence that you will win the lottery, since it becomes more likely that you will win, having a ticket, than not having one. But ordinarily you won’t win anyway, despite your evidence for it.