About Espers
Final Fantasy VI has the highest number of summon spells in any Final Fantasy allowing you to summon 27 total Espers. Throughout the game, you will encounter a variety of Espers. After finding an Esper, you will gain the ability to equip the Esper to learn magic spells. For example, the Esper Ramuh will teach Bolt. To equip the Espers, press "equip" in the summon window.
Esper Magic
Espers each come with specialized magic skills. Some Espers have fire magic, while others will have lightning-based magic. When the Esper is equipped, the player who has the Esper equipped will automatically earn the magic spell with enough magic points. Magic points are earned every time you defeat a magic enemy in battle.
Learning Rates
Each magic spell has a statistic next to it in the menu. For example, it may say "X10," "X2" or "X5." The X stands for the magic points times the rate of learning. Multiply the amount of magic points you receive from an enemy by the learn rate. If it takes 20 magic points to learn a spell that is set at a rate of X10 and you receive one magic point from an enemy, you will have to defeat two enemies to learn the spell.
Espers in Battle
Espers can be summoned in battle to perform the spells you want your characters to learn. Espers cost Magic Points to summon, so be aware of how many you have before summoning them. Go to "Magic" and press up at the menu. The Esper will be summoned. Using the Esper's magic will give you a preview of the magic spell you will be teaching to your character.