Which is the purpose of persuasive writing?

The answer is in the question. Persuasive writing is intended to persuade the reader of whatever the topic of writing is. Such as if you're writing about how healthy, let's say almonds, are. You'd need persuasive facts. If you were writing about how good a book you just read is, then you'd need to state certain parts of the book that persuade the reader it's compelling (all the while not spoiling the story.)