在 and location expressions
在 (zài) is used both as a verb and as a preposition. Its basic meaning is to express that something is located somewhere.
Examples:
他在家 (Tā zài jiā) He is at home (verb)
在哪儿 (Zài nǎr) Where is it? (verb)
在颐和园附近 (Zài Yíhéyuán fùjìn) (It) is close to the Summer Palace (verb)
他们在香山玩儿 (Tāmen zài Xiāngshān wánr) They are enjoying themselves in the Fragrant Mountain Park.
Location expressions
Location expressions follow the actual location. For example:
颐和园附近 (Yíhéyuán fùjìn) close to the Summer Palace
餐厅旁边 (cāntīng pángbiān) next to the restaurant
房间里面 (fángjiān lǐmiàn) inside the room