Learn Farsi: او کارمند است.

Yes! Farsi pronouns don't have gender. The word او can mean "he" or "she" depending entirely on who you are talking about. The context of your conversation will make it clear.

The lesson talks about attached verb endings like -am and -i. Why is است written as a completely separate word?

For "I am" and "you are", Farsi usually attaches the verb to the end of the previous word. But for "he/she/it is", the formal written word است stands alone. Just keep in mind that in casual, everyday speech, Iranians will often shorten it and attach it to the previous word as an -e sound.

Where is the word for "an" in this sentence?

Farsi doesn't use words like "a" or "an" when stating someone's job or profession. You simply state the profession right after the pronoun: او کارمند (He employee) + است (is).

Why does the verb است come at the very end of the sentence?

Unlike English, which usually puts the verb right after the subject, Farsi puts the main verb at the very end of the sentence. The literal word order here is "He" (او) + "employee" (کارمند) + "is" (است).