There are three common ways to express the position of an object in a sentence by using the verbs ‘在‘(zài), ‘有’(yǒu) and ‘是'(shì).
1/在 indicates the location or position of sth. or s.o.
Noun/Noun phrase (s.o/sth.) + 在(zài) + location word
刘老师在家里。Liú lǎoshī zài jiālǐ.
Teacher Lui is at home.
你的车在外面吗？Nǐ de chē zài wàimiàn ma?
Is your car outside?
银行在哪儿？Yínháng zài nǎ er?
Where is the bank?
2/有 indicates the existence of sth. or s.o. in particular place.
Location word + 有(yǒu) + Noun/noun phrase (s.o./sth.)
我家对面有一个公园。Wǒjiā duìmiàn yǒu yígè gōngyuán.
Across from our home, there is a park.
学校里有书店。Xuéxiào lǐ yǒu shūdiàn.
There is a bank next to the bookstore.
书店旁边有一个银行。Jiàoxué lóu qián yǒu Yígè yínháng.
There are many bicycles in front of the teaching building.
3/是 is used in a situation which we know there is s.o. or sth. in a particular place, but we want to know more specifically who he/she is or what it is.
Location word + 是(shì) + Noun/noun phrase(s.o./sth.)
这个包里是什么东西？Zhège bāo lǐ shì shénme dōngxi?
What’s in this bag?
这个包里是书和笔 。Zhège bāo lǐ shì shū hé bǐ.
They are books and pens in this bag.
孩子面前是妈妈。Háizi qiánbian shì māma.
In front of this kid is his mom.
超市对面是咖啡馆。Chāoshì duìmiàn shì kāfēi guǎn.
Across from the supermarket is a coffee house.