书包 (shūbāo) is a noun meaning "schoolbag" or "backpack." It is one of the first everyday objects learners encounter in school-related vocabulary, and commonly appears with verbs like 背 (bēi, "to carry on one's back").
你的书包怎么这么重,装了什么?
Nǐ de shūbāo zěnme zhème zhòng, zhuāng le shénme?
Why is your school bag so heavy? What did you put in it?
妈妈给我买了一个新书包。
Māma gěi wǒ mǎi le yí gè xīn shūbāo.
Mom bought me a new school bag.
他把课本放进书包就出门了。
Tā bǎ kèběn fàngjìn shūbāo jiù chūmén le.
He put his textbooks in his school bag and headed out.