Existence can also be expressed with the verb 是 shì , but the emphasis is somewhat different. With 有 yǒu the speaker is pointing out that something exists or is happening in a certain location or for a period of time and what is being described is usually of indefinite reference. Hence 有 yǒu is translated as ‘there is/are . . .’ in these expressions. 是 shì, on the other hand, as its basic meaning implies, has more of a defining function, and associates what exists or is happening directly with the location conveying at the same time the idea of pervasiveness. Hence, 是 shì is regularly used with 都 dōu or 全 quán ‘all, entirely’. Consider the contrasting sentences below:
Dì shàng dōu shì shuǐ。
The ground is covered with water. (lit. On the ground all is water.)
Dì shàng yǒu shuǐ。
There is water on the ground.
Shāng diàn lǐ dōu shì rén 。
The shop is/was crowded with people. (lit. In the shop all is people.)
Shāng diàn lǐ yǒu rén 。
There are/were people in the shop.
Tā shēn shàng quán shì ní 。
She was covered in mud. (lit. She on body all was mud.)
Tā shēn shàng yǒu ní 。
There is/was some mud on her/she has/had some mud on her.
Chú chuāng lǐ shì gè zhǒng gè yàng de shāng pǐn。
The shop window is full of goods of various kinds. (The display of goods is what you would expect in a shop window.)
Shāng diàn lǐ yǒu gè zhǒng gè yàng de shāng pǐn。
There are all kinds of goods in the shop. (The variety of goods is what interests you.)
Xià xīng qī liù zhè ér yǒu yī chǎng zú qiú sài 。
There’s a soccer match here next Saturday. (What’s happening here next Saturday is a soccer match.)
Xià xīng qī liù zhè ér shì yī chǎng zú qiú sài 。
It’s a soccer match here next Saturday. (What’s happening here next Saturday is a soccer match.)
Note from the two sets of examples below that grammatically the object of 有 yǒu is of indefinite reference but what follows 是 shì may be either definite or indefinite:
Sù shè hòu biān shì tú shū guǎn。
Behind the dormitory is the library.
Sù shè hòu biān shì yī gè tú shū guǎn。
Behind the dormitory is a library.
Sù shè hòu biān yǒu yī gè tú shū guǎn。
There is a library behind the dormitory.
Wò shì páng biān shì xǐ zǎo jiān。
Next to the bedroom is the bathroom.
Wò shì páng biān shì yī gè xǐ zǎo jiān。
Next to the bedroom is a bathroom.
Wò shì páng biān yǒu yī gè xǐ zǎo jiān。
There is a bathroom next to the bedroom.
 Yip, P. C., Rimmington, D., Xiaoming, Z., & Henson, R. (2009). Basic Chinese: a grammar and workbook. Taylor & Francis.