惧怕 is more formal and literary than 害怕 (hàipà), which is the everyday word for 'afraid.' Use 惧怕 in writing, speeches, or when expressing deep/serious fear.
usage
惧怕 takes a direct object: 惧怕黑暗 (fear darkness), 惧怕死亡 (fear death). It implies a deeper, more sustained fear than the casual 怕 (pà).
