These two patterns move the object before the verb - the only places normal Chinese abandons SVO. Both exist to say what happened TO something.
把 - handling the object
把 pulls the object forward so the verb can describe what was done with it: Subject + 把 + object + verb + result. 我把门关上了 (I closed the door), 请把书给我 (give me the book), 我把作业写完了. It is used when the result matters: not "I ate the apple" but "我把苹果吃完了 - finished it".
被 - the passive
被 marks the thing affected: Patient + 被 + doer + verb + result. 我的手机被偷了 (my phone got stolen), 他被老师表扬了 (he got praised). With no doer: 饭被吃完了. Colloquial synonyms 让 and 叫 do the same job in speech: 我的伞让同事拿走了.
When NOT to use them
Beginners overuse both. Plain SVO is still the default - say 我吃了饭, not 我把饭吃了, unless the point is the apple's fate. 被 especially is marked: mostly for adversative or noteworthy events, not every English passive. "The cake was eaten" as neutral narration is just 蛋糕吃完了.
The pattern they share
Both exist because the verb tail carries the interesting part - 关上了, 偷了, 表扬了. Word order serves focus: what you put last is what the sentence is about. 把 focuses the disposal, 被 focuses the patient's misbegotten day.
Common questions
When do you use 把 in Chinese?
When the point is what happened to the object: 我把窗户打开了 - "I opened the window", focusing on the result, not the act. Plain acts stay SVO: 我打开了窗户 is fine too.
How do you make a passive in Chinese?
Patient + 被 + doer + verb + result: 信被他拆了. No doer needed: 信被拆了. Colloquial 让/叫 replace 被 in speech.
Is 被 always negative?
Traditionally adversative (被偷, 被批评), but modern usage accepts good outcomes too (被表扬, 被邀请). The neutral-passive reading has spread through translation influence.