Learn Hardcore Korean: chilpan yeope sigyega geollyeo isseoyo. - There’s a clock hanging beside the blackboard.

걸려 있어요 literally means “is hung” or “is hanging.” It’s the descriptive/state form of the verb 걸다 (to hang) expressed as 걸리다 (to get hung) plus -어 있다 (to remain in that state). So you’re saying “the clock is in a hung-up state.”

Why is 걸려 있어요 used instead of just 걸어요?

걸어요 (active) means “I hang (something).”
걸려 있어요 (passive/state) describes the resulting state: “(Something) is hanging.”
Since the sentence tells us where the clock already is (hanging) rather than someone hanging it right now, we use 걸려 있다.

What role does 에 play in 칠판 옆에?

The particle 에 marks a location with verbs of existence or placement. Here 칠판 옆에 means “at/to the side of the blackboard.” Whenever you describe where something 있다, 걸려 있다, 앉아 있다, etc., you attach 에 to the location noun.

Why is 시계가 used (with the subject marker) instead of 시계를 (object marker)?

In 칠판 옆에 시계가 걸려 있어요, 시계 is not the object of an action but the subject of the state “is hanging.” You’re stating what exists in that state at that location, so you mark it with -가/이.

What’s the overall grammar pattern here?

It follows:
[Location] + 에 + [Subject] + 걸려 있다
This variant of the 있다-sentence adds information about the object’s condition or position (hung up) rather than mere existence.

Can I replace 걸려 있어요 with 매달려 있어요?

Yes. 매달리다 also means “to hang/be suspended.” For example:
칠판 옆에 시계가 매달려 있어요.
It’s perfectly natural and emphasizes that the clock is dangling or suspended.

What if I want to ask “What is hanging next to the blackboard?” in Korean?

You can say:
칠판 옆에 무엇이 걸려 있어요?
or more colloquially:
칠판 옆에 뭐가 걸려 있어요?

Could I use 곁에 instead of 옆에?

Yes. Both 옆에 and 곁에 mean “beside/next to.”

옆에 is more common in everyday speech.
곁에 can sound slightly more formal, poetic, or intimate, but the meaning remains “next to.”