What is a crypto pump-and-dump scam?

Excuse me, could you please explain what exactly is a crypto pump-and-dump scam? I've heard about it in the context of cryptocurrency trading but I'm not entirely sure how it works. Could you elaborate on the mechanics of such a scam and what investors should be wary of? I'm particularly interested in understanding how the perpetrators coordinate their actions and how they manipulate the market to their advantage.