两 + Measure Word + Noun
两 (liǎng) means 'two' and is used before measure words and nouns, unlike 二 (èr), which is used for counting and math. When specifying a quantity of two items, 两 is the correct choice, as in 两个人 (two people) or 两本书 (two books).
我买了两杯咖啡,一杯给你。
Wǒ mǎi le liǎng bēi kāfēi, yī bēi gěi nǐ.
I bought two cups of coffee, one for you.
他有两个姐姐和一个弟弟。
Tā yǒu liǎng gè jiějie hé yī gè dìdi.
He has two older sisters and one younger brother.
我们在那里住了两天。
Wǒmen zài nàlǐ zhù le liǎng tiān.
We stayed there for two days.