What is the difference between "understanding" (yafqahūn) and "knowing" (yaʿlamūn)?

The difference between "yafqahoon" (they understand deeply) and "ya'lamoon" (they know) is that fiqh (deep understanding) means a precise comprehension of hidden things and perceiving subtle meanings, whereas 'ilm (knowledge) is the perception of something as it truly is. Thus, fiqh is knowledge plus something more; it is used when the meaning involves a precision that requires deep understanding. As for "ya'lamoon," it is used when the matter simply requires perception.