Subject + 在 + Location
The verb 在 expresses that something exists or is located at a particular place. It functions similarly to "to be at" or "to be in" in English. For example, 他在家 means "He is at home" and 书在桌子上 means "The book is on the table."
我的猫在沙发上睡觉。
wǒ de māo zài shāfā shàng shuìjiào.
My cat is sleeping on the sofa.
他不在办公室,可能出去了。
tā bù zài bàngōngshì, kěnéng chūqù le.
He's not in the office; he probably went out.
你的钥匙在桌子上呢。
nǐ de yàoshi zài zhuōzi shàng ne.
Your keys are on the table.