How does the airdrop work?

Could you please explain how the airdrop mechanism operates? I'm quite curious about the process behind it. Could you elaborate on the steps involved in receiving free tokens through an airdrop? Also, is there a specific criterion or requirements that need to be met in order to qualify for an airdrop? Are there any risks involved that investors should be aware of? Lastly, do you think airdrops are a sustainable way for projects to attract users and build their communities? I'm keen to understand the pros and cons of this practice. Thank you for your time and insights.