Fiqh (فقه) is the most fundamental science one can undertake in learning after the science of ʿAqīdah; as when one has built & established the correct creed within their heart, they now move on to how to practice their religion in accordance with what Allāh has commanded & prohibited.
The Prophet ﷺ said:
Whoever Allāh intends good for, He grants him understanding of the religion.Ṣaḥīḥ al-Bukhārī #71, Ṣaḥīḥ Muslim #1037, Ṣaḥīḥ ibn Ḥibbān #89, al-Faqīh wa al-Mutafaqqih #17, al-Mu’jam al-Kabīr #871, al-Mu’jam aṣ-Ṣaghīr #810, Akhlāq ʿUlamā P. 27, Majmaʾ az-Zawāʾid 1/121, Jāmiʿ Bayān al-ʿĪlm wa al-Faḍlihi 1/24, Sharḥ Mushkil al-Athār 2/280, Musnad Abī Yaʿlā #5855, Sunan ad-Dārimī 1/74, Jāmiʿ at-Tirmidhī #2645, Sharḥ as-Sunnah #131, Musnad Aḥmad 4/99, al-Kāmil fī Ḍuʿafā‘ ar-Rijāl 1/179 | Muttafaqun Alayh, Ṣaḥīḥ to both Imām al-Bukhārī and Imām Muslim
My Ustādh mentioned to me that Fiqh has 3 meanings:
- Linguistically, “to understand”
- Technically, “knowledge of the rulings of the Sharīʾah that are action-based”
- Sharʾī, “the entirety of the religion whilst acting upon it” (which is the meaning intended in the Ḥadīth).
Shaykh Muḥammad ibn Ṣāliḥ al-‘Uthaymīn رحمه الله (d. 1421 AH/2001 CE) commentated on this Ḥadīth: “Understanding of the religion is better than understanding of current affairs, in opposition to what some of the youth think, that understanding current affairs is more important than understanding in the religion, when this is not the case. Understanding the religion is more important and it is binding upon a person to focus upon this.
As for understanding current affairs and the situation of the people, then this is a means of knowing what is appropriate from the various rulings and it is not the goal. The goal is understanding of the religion. So what will we benefit if we seek understanding of current affairs and do not seek understanding in the religion?
Also, sometimes understanding of current affairs prevents a person from that which is more important and preoccupies him with what is going on in the east and the west and so he forgets that which is more important.” 
And Allāh knows best.
May Allāh grant us Fiqh fī Dīn & make it easy for us to act upon our knowledge.
All praise is due to Allāh, may His peace & blessings be upon our final Prophet Muḥammad, his family, his companions, & all those who follow him in guidance.
 Sharḥ Ṣaḥīḥ al-Bukhārī (شرح صحيح البخاري) by Shaykh Muḥammad ibn Ṣāliḥ al-‘Uthaymīn | Hadith #71
Ṣafīullāh Labīb ibn Salīm ʿAbd al-Malik
21st of Rabīʿ al-ʾAwwal 1444