Peertube is the fediverse equivalent of youtube. So like Lemmy, you pick an instance, follow their rules, and post content. Like Lemmy, you will reach a smaller audience than the proprietary platform (in this case, youtube).
If you want to remove google from your life, or can’t be bothered with the anti consumer bullshit of proprietary platforms like youtube, then use Peertube.
If you don’t care about the above, and just want to reach a larger audience, use youtube.