You might have seen a quest, where if you stream a specific game to your friends you get a free in-game item, but these are not advertisements.

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Advertising is the practice and techniques employed to bring attention to a product or service. Advertising aims to put a product or service in the spotlight in hopes of drawing it attention from consumers

I have no interest in streaming "quested" games, and whatever deal Discord has done with the developer to encourage users to engage with such games (and by extension the game's microtransaction economy), and regardless of what they call it, is by definition an advertisement. If you can't see that, then you are an ad campaign exec's wet dream. Either that, or a troll.