Omae (おまえ) means “you” — a rough, casual “you”, used mostly by men, to close friends or to someone they look down on.
Textbooks teach あなた for “you” — then you watch one episode of anything and hear おまえ, きみ, てめえ… and nobody ever says あなた. What's going on?
The secret: Japanese avoids “you” entirely
The politest way to say “you” in Japanese is… not saying it. Use the person's name + さん, or drop it completely — the sentence usually works without it.
The “you” words, ranked by danger
あなた — textbook-polite but oddly distant; between spouses it's affectionate (“dear”), pointed at a stranger it can feel accusatory. きみ — soft and a little superior: bosses to juniors, and countless song lyrics. おまえ — rough and male-coded: between close friends it's camaraderie, aimed at a stranger it's a challenge. てめえ — fight scene. If you hear this one, someone is about to get punched.
おまえ！
Hey, omae!
Rude!! I have a name, you know. 😾
…ゆきさん、 すみません。
...Sorry, Yuki-san.
So what should YOU say?
Real life isn't an anime battle: default to name + さん, exactly as Chapter 1 of the course teaches. Anime writers hand out おまえ because it instantly shows rivalry, intimacy or aggression — it's characterisation, not a model for the office.