Jest kolejka oczekujących.

Here jest means there is or there exists.

Polish often uses jest in this existential way:

• Jest problem. = There is a problem.
• Jest kolejka. = There is a queue.

Unlike English, Polish does not need a dummy subject like there.

Because the grammatical subject is kolejka, which is singular.

So the structure is basically:

• kolejka = queue, line
• oczekujących = of those waiting

In other words, Polish is saying there is a queue of waiting people, and the verb agrees with queue, not with the people inside that queue.

Because after existential jest, the noun is normally in the nominative case.

So:

• Jest kolejka. = There is a queue.

Here kolejka is the subject of the sentence, so nominative is correct.

A useful contrast:

• Nie ma kolejki. = There is no queue.

With nie ma, Polish usually switches to the genitive, which is why you get kolejki there.

Here kolejka means queue or line.

It is the normal everyday Polish word for a line of people or things waiting.

Depending on context, kolejka can have other meanings too, but in this sentence the meaning is clearly queue/line.

Oczekujących comes from oczekujący, which means waiting, awaiting, or sometimes expecting.

In this sentence it is in the genitive plural:

• kolejka oczekujących

Literally, that means something like:

• a queue of waiting ones
• more naturally, a queue of people who are waiting

Polish often uses a genitive phrase after a noun to show what kind of group or collection it is.

Grammatically, it is an adjective-like participial form, but here it is being used like a noun.

So it means:

• those who are waiting
• the waiting people

This is very common in Polish. A descriptive word can stand on its own if the noun is understood from context.

You can think of an implied word such as:

• osób = people
• ludzi = people

But Polish does not need to say that explicitly here.

Often yes, but the tone changes a little.

• czekać = to wait
• oczekiwać = to wait for, await, sometimes expect

Czekać is usually more everyday and conversational. Oczekiwać can sound a bit more formal or official.

So:

• kolejka czekających may be possible in some contexts
• kolejka oczekujących sounds more formal or institutional

The exact choice depends on context and style.

Because Polish has no articles.

So kolejka can mean:

• a queue
• the queue

Context tells you which one is meant.

This is normal in Polish, and learners just have to get used to relying more on context than in English.

Yes, Polish word order is fairly flexible, but the order here is natural for introducing existence.

Starting with jest gives the sentence a clear there is feeling:

• Jest kolejka oczekujących. = There is a queue of people waiting.

If you change the order, the emphasis changes too. This version is good when you want to present the queue as new information.

Not in the same way a normal adjective would.

A direct adjective agreeing with kolejka would have to match it in gender, number, and case, for example:

• długa kolejka = a long queue

But oczekujących does not match kolejka that way. Instead, it forms a separate genitive phrase:

• kolejka oczekujących = a queue of those waiting

So it is not the queue that is waiting. It is the queue belonging to / made up of the waiting people.