They are tricky and sometimes difficult even for native speakers to use properly. Both of them are used when we talk to superiors. They are differentiated by subject, WHO does/acts something in a sentence. for example; 食べる (eat) ： basic form 召し上がる (eat) ： honorific form / SOMEONE who is superior eats いただく（eat）： humble form / I ( or WE) eat Polite form (丁寧語) It's just a polite way to talk. i.g. （あなたは）何を食べましたか？ =　What did you eat? （私は）先に食べました. = I ate it (before you do). Honorific form (尊敬語) It is used when talking about an action of high-ranking people, superiors and customers. i.g. （あなたは）何を召し上がりましたか？　 = What did YOU eat? Humble form (謙譲語) It is used when I (or we) describe something about myself (ourselves) to superiors or high-ranking people. i.g. （私は）先にいただきました。　＝ I ate it (before you do). * We usually say "いただきます" out of habit before eating as you might know, and it's a humble word. ----- Folllowing is a Japanese web page about those words, which is simple but well organized. http://park2.wakwak.com/~lion/benkyou/kotoba-tukaiwake.htm