According to Sanderson's Law of Magic, what is the difference between hard and soft magic?

The idea of hard magic and soft magic was popularized by Sanderson for world building and creating magic systems in fictional settings. The terminology of hard and soft originate from hard and soft sciences, which lends itself towards hard science fiction and soft science fiction. Both terms are approximate ways of characterizing two ends of a spectrum. Hard magic systems follow specific rules, the magic is controlled and explained to the reader in the narrative detailing the mechanics behind the way the magic 'works' and can be used for building settings that revolve around the magic system. Soft magic systems may not have clearly defined rules or limitations, or they may provide limited exposition regarding their workings. They are used to create a sense of wonder to the reader.

Hard magic is always strictly constrained by a set of rules which can simulate a more ordered world to the reader, while soft magic if more flexible, has no clearly defined limitations and can be used to imbue a sense of wonder to the reader.