Learn Hardcore Korean: setakso yeope uchegugi isseoyo. - There is a post office next to the laundry shop.

옆 literally means “side,” and when you add the location particle 에 it becomes 옆에, meaning “at the side of.” Idiomatically, 옆에 = “next to” or “beside.”

Why is there no particle attached to 세탁소 before 옆에?

Here 세탁소 (dry cleaner) is just a modifier describing 옆 (side). Together they form the compound location phrase 세탁소 옆 (“the side of the dry cleaner”). You don’t use 은/이 or 는/가 on 세탁소 because it isn’t the main subject—it’s part of the location description.

Why is 우체국 followed by 이 instead of 은?

이/가 marks the subject when you’re presenting new or focal information. In existential sentences with 있다, you almost always use 이/가. Using 은 (the topic marker) would suggest you’re contrasting or returning to a topic you’ve already introduced.

What is the role of 있어요 in this sentence?

있어요 is the polite present form of the verb 있다, which here means “to exist” or “to be located.” So 우체국이 있어요 literally means “A post office exists” or “There is a post office.”

Can I reorder the sentence as 우체국이 세탁소 옆에 있어요?

Yes. Korean allows flexible word order. Both

세탁소 옆에 우체국이 있어요 (location first) and
우체국이 세탁소 옆에 있어요 (subject first)
are grammatically correct and mean “The post office is next to the dry cleaner.” The difference is only a slight shift in emphasis.

How would I ask “Is there a post office next to the dry cleaner?” in polite speech?

You have two common options:
• Rising intonation on 있어요:
세탁소 옆에 우체국이 있어요?
• More formal ending with -습니까:
세탁소 옆에 우체국이 있습니까?