What is the difference between Fiqh and Usul al-Fiqh?

Fiqh (Islamic jurisprudence) is the knowledge of the Sharia rulings derived from detailed evidence. It is the knowledge of the Sharia ruling, whether it is haram (forbidden), wajib (obligatory), mustahabb (recommended), makrooh (disliked), or mubah (permissible). As for Usul al-Fiqh (principles of Islamic jurisprudence), it consists of the rules whose study leads to the derivation of rulings from their detailed evidence, or it is the knowledge of these rules. It clarifies for the jurist the method he must adhere to in extracting rulings from their evidence.