1. in the tranditional and standard chinese, “被”=“be + past participle”, it can represent the passive tense. you can learn its usage from the examples above. Beside, "被" can also be a noun, which means quilt, blanket especially covered on the bed.
2. 【this part is what i want to add】in informal chinese, espcially the internet slang, "被"="be forced to do sth with reluctant will"
e.g. “被自愿”=“be forced to be willing to do sth (actually be reluctant to do that)”
"被捐款" =“be forced to donate money (actually be reluctant to donate money at all)”