Learn Dutch: 's Nachts wordt er niet gepresenteerd. - At night, people do not present.

This is the impersonal passive voice. Dutch uses worden (to be) plus er (there) and a past participle to describe an action happening without mentioning who is doing it. It translates literally to "there is not presented", which is how Dutch naturally expresses "people don't present" or "no presenting happens".

What is the subject of this sentence?

The word er acts as a "dummy subject" here. Because the passive voice removes the actual people doing the presenting, the sentence still needs a grammatical subject to be complete. Dutch uses er for this purpose when there isn't a specific object being acted upon.

Why is the verb wordt placed before the subject er?

This is because of the V2 (verb second) rule. The sentence starts with the time phrase 's Nachts. In Dutch, the main conjugated verb (wordt) must always take the second position, so the subject (er) swaps places with the verb and comes right after it.

Why does 's Nachts have an apostrophe and a lowercase 's' at the beginning?

The 's is a short form of an old Dutch word des (meaning "of the"). So 's nachts originally meant "of the night". When a sentence starts with this little 's, it stays lowercase, and the first letter of the main word (Nachts) gets capitalized instead!