A toadstone is a special kind of shiny rock that some people used to believe had magical powers. They thought that if they carried a toadstone with them, it would protect them from bad things happening, like getting sick or getting hurt.
Now, the thing is, toadstones don't actually come from toads! They're really just a special kind of fossil that used to be found in rocks near the ocean. These fossils looked a bit like a tooth or a tiny horn, and people thought they came from the head of a toad.
Even though we now know that toadstones aren't magical and didn't actually come from toads, they are still pretty neat to look at and can remind us of how people used to believe in magic a long time ago.