Final Fantasy VII Remake players can learn four very powerful Enemy Skills by defeating the creature that has one.
You must learn all the enemy skills to get the Silver Trophy Eclectic Mastery. To learn enemy techniques you must first unlock and equip the Enemy Skill Matter.
To obtain this subject, you must purchase it from Chadley after completing file no. 16 of the research files. The first opportunity to do so is in Chapter 13, here you can find it next to the Materia Shop in Sector 5 of the Basics.