存现句【cúnxiànjù】

An existential sentence – one that says what is somewhere – puts the place first, the verb in the middle, and the thing last. The thing is new to the listener, so it usually comes with a number and measure word: 一本书, 两个人.

What is there: verb + 着

A verb of placing or posture with 着 says what is in a place and how it's there: lying, hanging, standing, sitting.

有 says only that something is there. The verb + 着 version adds how.

What appeared or left: verb + 了

A verb of coming, going or losing with 了 says something has turned up or gone. The place, or a time, comes first.

A directional complement – 过来, 出来, 过去 after the verb, saying which way it moves – shows something coming into view.

No 在 at the start

The place is the subject here, so it doesn't take 在.

• × 在桌子上放着一本书 → 桌子上放着一本书

English order

English says "a guest came to the house". Carried over, the thing goes first and the place last.

• × 一位客人来了家里 → 家里来了一位客人

When the thing is already known – "the book", "my keys" – it goes first in an ordinary sentence instead: 书在桌子上.